Compared to the reptile keeper, the amphibian keeper is faced with different challenges of water quality maintenance and perhaps finds closer kinship with the aquarist. Reptiles have thick, impermeable skins and can tolerate poor water conditions better than fish and amphibians. Consequently, most reptile keepers simply change their captive’s water when it is visibly fouled. Amphibians have thin, permeable skins, similar to the gills of fish, through which they absorb some of their water and oxygen (drink and breathe). Unfortunately, their thin skin also readily absorbs toxins, so water purity (visible and not) is of the utmost importance. The amphibian keeper quickly finds that successful husbandry can depend largely on balancing water chemistry and maintaining water quality. This chapter is intended to provide the reader with enough basic knowledge about water quality and filtration equipment to set-up and maintain functional aquatic and semi-aquatic systems for captive amphibians.
THE SOURCE
Municipal Tap Water
Water quality obviously begins with the water used to fill the tank initially. In most regions, simply aging and aerating tap water for 24 hours will be all that is required to condition it for use with amphibians. This treatment will drive off harmful gases (carbon dioxide, nitrogen, hydrogen sulfide) and bring desired gases (oxygen) into equilibrium. However, one will also want to buy kits or meters to test levels of pH and general hardness to be sure that these parameters are within acceptable limits. [These and other products mentioned below are readily available at local pet stores or through some of the pet supply companies listed in Appendix A.] Chlorine/Chloramine Tap water must be treated to remove chlorine and/or chloramine, which are added to municipal water supplies to kill potential pathogens. Although they are added in small enough quantities that they are not harmful to mammals and reptiles, they are extremely toxic to amphibians. There are many commercial products available for chlorine neutralization; sodium thiosulfate in pure form is best, and this chemical is the primary ingredient in most commercial tap water treatments. However, the easiest treatment is simply aging and vigorous aeration, as chlorine will generally dissipate from aerated water within one day. Dedicate a water-conditioning tank where water can be so treated for a minimum of 24 hours before use. Alternatively, one can run the water through a carbon filter to remove chlorine, but it is difficult to determine when chemical filters are saturated and in need of replacement (see discussion of chemical filtration below).
Chloramine is replacing chlorine as a tap water disinfectant in many parts of the country, as the former tends to be more stable in solution, but it is doubly problematic for the aquazoologist. Chloramine breaks down gradually to produce chlorine and ammonia, both of which are highly toxic to amphibians and must be removed. One must find out which chemical the local water municipality uses and treat the water accordingly. Ammonia in the water-aging tank is probably best treated with chemical conditioners, such as zeolite or AmQuel®, with proper testing before use. Biofilters, although ideal for removing ammonia from an established aquarium (see discussion of biological filtration below), would be susceptible to any chlorine or gas supersaturation in the aging tank. Dissolved oxygen
All amphibians can absorb some oxygen across their skin. Most aquatic amphibians have lungs to supplement cutaneous respiration when dissolved oxygen (DO) is insufficient. However, many are lungless, including most larvae, and DO is as important for them as it is for fish. Oxygen starved amphibians constantly wave their gills or make frantic runs to the surface for air, and the engorged gills turn crimson with blood. Similarly, amphibians with ‘fleshy’ skin, such as hellbenders, giant salamanders, hairy frogs, and Lake Titicaca frogs, will rock back and forth to break up the boundary layers around their bodies when DO is low.
Water from the tap has typically not been exposed to air for some time and the DO can be dangerously low. As with dechlorination, the simplest treatment is aging and aeration, and a day is generally sufficient to bring gas concentrations back to normal.
Inside the aquarium, DO is consumed by the animals, the plants, and the bacteria in the biological filter. It is generally not necessary to monitor DO, but one should take certain measures to ensure that it remains at sufficient levels. Adequate aeration is most important. The air bubbles do not drive oxygen into solution, rather they increase circulation and disrupt the air-water interface where the majority of gas exchange takes place. Allowing the water returning from the filter to splash onto the water’s surface will also help disrupt the interface and facilitate gas exchange. Along these lines, shallow, wide tanks have greater surface area for a given volume than tall, narrow tanks and are therefore better for gas exchange.
Temperature profoundly affects DO. Warm water holds significantly less dissolved gases than cold, and animal densities and/or aeration levels should be adjusted accordingly. Plants also have a major impact on DO. Throughout the day, plants produce more oxygen than they consume and DO gradually rises. However, at night, the plants only consume oxygen and DO levels can reach critically low levels by morning. In smaller, heavily planted or heavily stocked systems where this might be problematic, an extra aerator on a timer can help ensure adequate mixing throughout the night. Gas supersaturation
Tap water can be supersaturated with dissolved gases (especially nitrogen and carbon dioxide, but sometimes even oxygen), which when exposed to aquatic animals, can cause gas-bubble disease, a condition similar to the bends in divers. Supersaturation is generally problematic only in the winter when the water is especially cold and capable of holding even more gas. This condition is exacerbated when incoming water is pressurized from being pumped. The only treatment for supersaturation is time, which can be lessened with vigorous aeration to drive out the dissolved gasses (a process called off-gassing or degassing) and the application of heat. Aerating water to remove gas might seem counterintuitive, but remember that the water is supersaturated from being under pressure, and aeration at atmospheric pressure will bring the water back to equilibrium with normal air. Heating the water to room temperature will lower its ability to hold dissolved gases. Anyone who has allowed a tankfull of cold tap water to heat-up and observed the formation of tiny air bubbles on the glass is familiar with this process. Similarly, water heated for boiling first relinquishes its dissolved gas as tiny bubbles on the vessel walls before reaching a roiling boil.
pH
pH describes the number of hydrogen ions (free protons) in the water and is measured on a scale from 0-14. The lower the pH, the greater the hydrogen ion concentration and the more acidic the water; a higher pH indicates fewer hydrogen ions and more basic water. pH, and perhaps more importantly, pH stability, are critical, and a good pH meter (e.g., PinPoint), is a wise investment. Meter measurements are much more precise and consistent than those of cheap color-change kits. However, probes must be calibrated monthly and replaced at least yearly, making them high maintenance and expensive.
A pH of 7 is considered neutral, and most amphibians prosper at pH 6.0-8.0. An excessively high or low pH (>9 or <5) can negatively impact an animal’s physiology, primarily by changing the conformation of enzymes, but also by altering the ability of the blood to transport respiratory gases and by interfering with membrane transport.
pH also profoundly affects ammonia toxicity. At a ‘lower’ pH, ammonia binds a hydrogen ion and exists in its ionic form, NH4+. This ammonium ion is much less toxic than the form that occurs at a ‘higher’ pH, NH3. The concentration of the two forms is equal at approximately pH = 9.3. Above this, the more toxic form predominates. Fortunately, most aquatic systems function best at a pH well below 9.5. However, even at a lower pH, NH3 is still present in some concentration.
Because of the interaction between pH and ammonia, a concentration of ammonia that is relatively harmless at pH 6.5 can be deadly if the pH rises to 7.5. The idealist will say ‘keep the ammonia concentration at zero and pH/ammonia interactions will never be a problem’ but the pragmatic knows that ammonia spikes do sometimes occur and tries to keep the pH near or slightly below neutral to minimize their impact. Remember this interaction when receiving a shipment of aquatic animals. The CO2 and ammonia concentrations in the shipping water are likely high and the pH low. Float the bag to achieve a common temperature, but do not mix bag and tank waters. The higher pH of the tank water can cause the ammonium in the bag to convert to more toxic ammonia and kill the new arrivals. Simply pour the temperature-acclimated animals into a net over a bucket or sink and add only the animals to the tank.
Changing the pH of tap water is possible, but maintaining new levels can be labor intensive with much monitoring and tweaking. Perhaps changes are best reserved for particularly sensitive species or in areas where tap-water pH is far from neutral. pH can be lowered by adding small amounts of dilute acid to the system. The safest way to do this is to add a nylon bag of peat or sphagnum moss to the filter or tank. The waterlogged moss will release tannic and humic acids into the system, gradually and naturally lowering the pH, and also the hardness. Bubbling carbon dioxide into the water will also lower the pH and greatly enhance the growth of plants. Diluting tap water with distilled, deionized, or reverse osmosis water will lower pH, but it will also lower pH stability (carbonate hardness). pH can be raised by adding small amounts of dilute base to the system. Sodium bicarbonate (baking soda) is inexpensive and very effective. Start with a small dose (1/8 level teaspoon per 20 gallons) and wait 24 hours for the pH to stabilize before testing/tweaking again. Avoid commercial pH buffers, which can be high in phosphates and cause algae blooms.
The inexperienced must proceed with caution: always change the pH in small increments in a tank with living animals to minimize physiologic disturbance. pH changes on a logarithmic scale, so changes do not lend themselves to ‘common sense.’ A pH of 6 is not just a little lower than a pH of 7, it is 10 times lower, and 100 times lower than a pH of 8. Consequently, it will take a lot more acid to drop from 8 to 7 than from 7 to 6.
The pH in most closed aquatic systems will naturally fall over time. Decomposition of detritus (uneaten food, feces, shed skin, and dead plant material), respiration of the animals, and biological filtration (bacterial respiration) all bring down the pH. A good mechanical filter that is cleaned regularly, weekly water changes, and good aeration and circulation will help keep ‘pH fallout’ in check.
General hardness General hardness (GH) is a measure of the amount of minerals dissolved in the water, primarily calcium and magnesium. Many amphibians prefer moderately soft water; however, it is always best to consider the natural habitat of the species in question. Is the animal from a river fed primarily by rainwater (soft), or from lakes in limestone bedrock (hard)? Water can be hardened by adding calcium and magnesium salts: about one gram of mixed calcium chloride and magnesium sulfate (mixed 6:7 by weight) will raise 10 gallons of water by 1 degree general hardness (1 dGH) and provide an ideal calcium to magnesium ratio (3:1). Water can be softened by diluting with distilled, reverse osmosis, or deionized water. Unlike with pH, changes in hardness occur linearly, so cutting 6 dGH water by 50% gives 3 dGH. Changing water hardness can also affect pH, and vice versa. Make changes slowly and test often. Beware when using household water softeners – they replace hard water minerals with salt, which can dehydrate amphibians.
Temperature and plumbing
Always use water from the cold tap and heat it (or allow it to warm to room temperature) in the aging tank. Water that passes through a hot water heater absorbs toxic heavy metals and minerals, which concentrate there like scale in a teapot. Also, hot water is more likely to leach toxins from metal pipes. Lead pipes are problematic at any temperature, for animals and humans, and should be replaced. Low-dose lead poisoning causes long-term neurologic problems. Water that sits in copper pipes overnight can absorb enough copper to cause acute copper toxicity and death in amphibians. Chronic copper exposure in some animals has been found to cause development of copper crystals in the liver. Old copper pipes, which might form an oxidized scale on the inside, seem less likely to leach than new ones. Running the water for several minutes before use to flush the system is a temporary partial fix. Using plastic (PVC or CPVC) pipes eliminates the problem of leached heavy metals and is ideal for cold water applications, but running hot water through them might cause the leaching of toxic vinyl chlorides. CPVC is more heat-resistant than PVC; flexible PVC (rubber hose) is worst.
Well Water
Well water can be an acceptable source for use with amphibians, but again, one must test pH, hardness, and in coastal areas, salinity. In some regions, especially where water is pumped up from limestone bedrock, well water can be too hard and the pH too high -- test and treat accordingly. In agricultural areas, well water can also be high in phosphates and nitrates from fertilizers that seep into the water table. These substances cause algae blooms and at higher concentrations are toxic to animals, so testing well water for them is also recommended. Again, carbon can help keep pollutants in check, but see the caveats in the section on chemical filtration.
Well water can also be saturated with nitrogen and carbon dioxide, devoid of oxygen, and even contain lethal quantities of hydrogen sulfide. Vigorously aerating the water for at least a day before use will drive off the nitrogen, carbon dioxide, and hydrogen sulfide, as well as raise the oxygen content. Well water can also contain unoxidized ferric (iron) compounds, which react with oxygen when exposed and precipitate from solution. If the precipitate settles on the gills or skin of fish and amphibians, it can cause irritation, excess mucus production, and even suffocation. Again, aerating the water before use will cause this reaction to occur away from the animals; the precipitate can then be filtered out or allowed to settle.
Rain Water
Rainwater is naturally soft, perhaps too soft for some species. Test hardness and, if near a city where pollution and acidification are problematic, pH. Also, one must consider how the rain is collected. Do not collect rain from a galvanized metal roof or one that has otherwise been treated chemically. A large tarp tied to four posts and angled at one end to drain into a plastic 50-gallon drum is effective, albeit not very attractive. Such rain barrels can also be a great source of mosquito larvae.
Similarly, water that collects in natural basins, such as ponds, streams, and lakes, can be a good source of acceptable water. One must check where the water is coming from – is it draining from a large parking lot covered with oil spills, or from a commercial farmer’s field where it might have picked up fertilizers, herbicides, or insecticides? Another thing to consider is that this water might be contaminated with diseases or parasites from wild animals. Alternatively, the ‘stuff’ living in the water could be what makes it great. Natural pools teeming with invertebrate life offer more diversity and nutrition than could ever be cultured indoors.
Bottled Water
If tap water is not acceptable and a reliable outdoor supply is unavailable, bottled water might be an acceptable alternative. Again, the pH and hardness, and even the chlorine level, must be tested. Bottled spring water pumped up through bedrock can be unacceptably hard and basic. Furthermore, purity-testing requirements for bottled water are not as strict as for tap water. A recent survey by the Natural Resources Defense Council showed that 1 in 3 samples of bottled water contained contaminants, including synthetic organic chemicals, coliform bacteria, or even arsenic. In some cases, bottled ‘spring’ water was shown to be simply bottled tap water. Consult the
NRDC website
or write/call NRDC Headquarters, 40 West 20th St., New York, NY 10011, 212-727-2700, to get the results for a particular bottled water source.
Reverse Osmosis
The safest and most consistent way to ensure a constant supply of perfect water is to make it from scratch. Reverse osmosis filters use high pressure to force water through a semipermeable membrane, leaving practically everything that was suspended and dissolved in the water behind. Osmosis is the tendency for water to move from areas where the ion concentrations are relatively low to where they are relatively high. This natural law brings solutions into equilibrium by making them equally concentrated. The process of reverse osmosis uses high pressure to make water do just the opposite, i.e., flow away from its dissolved ions. RO filters are now commonly available as affordable models that fit under a sink and produce modest amounts of purified water in a day.
SpectraPure
and
Kent Marine
are popular manufacturers among zookeepers and hobbyists. RO water is essentially pure, too pure in fact to be used as is. It must be ‘reconstituted’ by adding back a few beneficial trace elements, otherwise this ultrapure water will literally blow up your amphibian and suck the ions right out of it. The RO water moves across an amphibian’s skin and into its body in an attempt to ‘dilute’ the concentrated ions there (again, osmosis). As a result, the animals might not be able to excrete all the excess water and they swell up (a condition called edema). Moreover, it is taxing to the kidneys. They are unable to keep up with the high filtration demand, and many ions are lost in the excess urine. Kidney failure is not an uncommon outcome of keeping amphibians in pure water.
Commercial additives containing the requisite trace elements are available, but seem to provide little pH buffering capacity (carbonate hardness or KH, sometimes called alkalinity). Test the reconstituted water for carbonate hardness and add sodium bicarbonate (baking soda) to raise the KH and stabilize pH. One teaspoon of baking soda will give 4 degrees (72 ppm) carbonate hardness to 13 gallons, but will also raise the pH significantly. Allow the pH some time to equilibrate, and adjust the dose to give the desired pH and pH stability.
The following do-it-yourself reconstitution formula allows finer control and can be tailored to meet individual needs. This mix was developed largely by fish and aquatic plant hobbyists but fine-tuned for amphibians:
100 gallons of RO water 15.0 g calcium chloride CaCl2 17.6 g magnesium sulfate MgSO4·7H20 13.6 g potassium bicarbonate KHCO3 11.3 g sodium bicarbonate NaHCO3 0.5 g commercial trace element mix
Dissolving the crystals in a jar of water first and then adding the solution to the storage tank will ensure proper mixing. The final composition is similar to moderately soft fresh river water (Appendix B), with roughly 3 degrees of general hardness and 2 degrees carbonate hardness, ideal Ca:Mg (3:1) and Na:(Ca+Mg+K) (1:4) ratios, and depending on aeration levels, a pH around 7.4. Reducing the calcium and magnesium will soften the water, and reducing the bicarbonates will reduce the pH (and unfortunately the pH stability), and the product will be a better approximation of Amazon water. For smaller volumes, the formula can be cut proportionally to suit individual needs (see Appendix C for calculations).
The trace element mix provides small quantities of elements that are usually present in low concentrations (hence trace) in most bodies of water. Although deadly at higher concentrations, they seem to be necessary in small amounts for normal growth and development and they greatly enhance plant growth. The quantity recommended yields 0.1 ppm iron, the ideal for aquatic plants. Trace element mixes are available through hydroponics suppliers (e.g., #6 chelate trace element from
Homegrown Hydroponics).
RO filters do not remove everything. Some nitrates, phosphates, and silicates, which can be present in tap water at low concentrations, can pass through. Although not toxic at low levels, these substances can cause unsightly algae blooms. A deionizing (DI) filter cartridge used in conjunction with the RO filter will help eliminate nitrates and phosphates, should they prove problematic. A DI filter uses chemical resins that must be periodically regenerated or replaced. Special silica-removing RO membranes are available, but this substance is generally only a problem in salt-water aquaria.
Reconstituted water should be used to fill tanks initially and for water changes. In primarily aquatic systems that (a) do not receive regular, large water changes, and/or (b) have a high rate of evaporation due to powerful lights, splashing, overhead air circulation, etc., only pure RO water should be used to top-off when water evaporates (Appendix D).
RO filter membranes do eventually go bad, so test the product water periodically with a conductivity meter, or purchase a model with a built-in purity meter. Using a water softener inline before the RO unit will extend the life of the (expensive) filter membrane: removing salt is easier on the membrane than removing hard-water minerals. RO membranes are also highly sensitive to chlorine, and most manufacturers offer in-line carbon filters to be placed upstream from the RO filter. Using carbon in this fashion will remove chlorine from the water supply and reduce or eliminate the need for chemical filtration in the individual tanks, but one must regularly replace the carbon cartridge according to the manufacturer’s recommendations.
FILTRATION
Once the tank is full of conditioned water, the initial quality is maintained with filtration, testing, and regular water changes. There are three categories of water filtration to consider: mechanical, chemical, and biological.
Mechanical filtration
Once the tank is full of conditioned water, the initial quality is maintained with filtration, testing, and regular water changes. There are three categories of water filtration to consider: mechanical, chemical, and biological.
Larger mechanical filters designed for pools employ sand or diatomaceous earth as a medium and are appropriate for large tanks with several hundred gallons and up. These media form dense beds that trap very fine particulate matter and leave the water passing through them crystal clear. Because they are so efficient at removing suspended particles, they must be cleaned frequently, as often as once a day in systems with heavy bioloads. Cleaning is easily accomplished by simply turning a lever to reverse water flow and ‘backflush’ the system down a drain. If they are not regularly cleaned, sand filters tend to become clogged with detritus and bacterial colonies that cause the sand to clump, making backflushing ineffective. Backflush water will flow around the clumps (channeling), leaving the majority of the waste behind. Even when cleaned regularly, it is generally held that at least 2 tankfulls of water are required at backflushing to remove 90% of the trapped detritus. This means large volumes of treated replacement water must be on hand. Further, sand filters are usually opaque, making visual inspection of the contents during operation impossible. Because of their high maintenance and large backflush volumes, these filters are not very convenient. They also require some basic plumbing skills to install. For larger applications, several large canisters (e.g., Ocean Clear®) can instead be plumbed in parallel.
Note that all mechanical filters only trap waste particles – they do not remove them from the water system. Unless the filter medium is changed or cleaned regularly (at least twice weekly; daily is best), the filtered material will decompose in the filter and release toxins back into the circulating water. The longer the solids are in the water, the more they will liquefy and degrade water quality. It is much easier to deal with mechanical waste than chemical waste.
Chemical filtration
Many common toxins can be removed using the second type of filtration, chemical filtration. Chemical filters use media that chemically bind the toxins and remove them from the circulating water. One popular chemical medium is activated carbon, which removes a wide variety of organic toxins, chlorine, chloramine, pesticides, colors, odors, and heavy metals. However, chemical media can become saturated with toxins, and if they are not changed regularly they will begin releasing those toxins back into the water. Unlike mechanical filters, one can’t see when a chemical filter needs changing. It is generally recommended that chemical media be changed every 2-4 weeks, but this will vary widely depending on the amount of media in the filter and the chemical load in the water. Some experts recommend using only a small amount of carbon every few weeks for a couple days at a time, discarding the carbon after each use.
One of the most problematic toxins, ammonia, results from decomposition of uneaten food, feces, and other detritus. Many fish and aquatic amphibians also excrete ammonia as their end-product of protein digestion, just as urea is the nitrogenous waste of mammals and uric acid of birds and reptiles. Ammonia is colorless and odorless (at the concentrations considered here) and unless one is specifically testing for it (highly recommended), it is impossible to detect. One need not worry about exact concentrations (any ammonia is too much ammonia), and cheap color indicator tests are therefore sufficient. The color changes from clear to yellow in proportion to the ammonia concentration; in essence, the more it looks like urine, the more it is urine. Ammonia can be chemically filtered with media like zeolite or Ammo-Chips®, but these substances must be replaced regularly as it is impossible to tell when they are becoming saturated. Ammonia can also be kept in check with regular water changes, but these might be required on a daily basis for tanks with heavy bioloads.
One of the most problematic toxins, ammonia, results from decomposition of uneaten food, feces, and other detritus. Many fish and aquatic amphibians also excrete ammonia as their end-product of protein digestion, just as urea is the nitrogenous waste of mammals and uric acid of birds and reptiles. Ammonia is colorless and odorless (at the concentrations considered here) and unless one is specifically testing for it (highly recommended), it is impossible to detect. One need not worry about exact concentrations (any ammonia is too much ammonia), and cheap color indicator tests are therefore sufficient. The color changes from clear to yellow in proportion to the ammonia concentration; in essence, the more it looks like urine, the more it is urine. Ammonia can be chemically filtered with media like zeolite or Ammo-Chips®, but these substances must be replaced regularly as it is impossible to tell when they are becoming saturated. Ammonia can also be kept in check with regular water changes, but these might be required on a daily basis for tanks with heavy bioloads.
Biological filtration Basic startup
A more effective way to eliminate ammonia is to use biofiltration. Biofilters promote and support the growth of nitrifying bacteria, organisms that break down toxic ammonia into less toxic nitrite, and nitrite into less toxic nitrate. These bacteria are present everywhere and one need only provide a suitable environment for them to grow and allow them ample time (usually 3-6 weeks at tropical temperatures) for them to colonize the filter. Spiking the new tank with some gravel (and the attached bacteria) from an established tank will usually accelerate the process. The bioload (number of animals) should be kept low at first and the ammonia level frequently tested while the biofilter is becoming established.
Although nitrites tend to cycle with ammonia and testing only for the more toxic ammonia is generally sufficient, nitrites can present problems of their own. The bacteria that convert nitrites to nitrates require some phosphate in the water; if ammonia has spiked and waned but nitrites continue peaking, adding some phosphate is often enough to bring things inline. Excess nitrites can enter fish and amphibians and bind to the hemoglobin, interfering with respiration (brown-blood disease). Such animals will increase buccal pumping, gill waving, and/or trips to the surface for air, even though the water may be well oxygenated.
Nitrate, the end-product of nitrification, can be broken down to gaseous nitrogen by certain anaerobic bacteria, it can be utilized by living plants, or it can be controlled through regular water changes.
Hydrogen ions are also a product of biological filtration, so one must regularly test pH. Under certain circumstances (e.g., soft water, high bioload), a good biofilter can bring down the pH in a matter of days.
Cycling without fish
Instead of waiting 3-6 weeks while gradually increasing the bioload, one can cycle the tank without animals so that the biofilter will be established when the animals arrive. This technique has the additional bonus that no animals are put at risk while the filter is becoming established and toxins are spiking. A Ph.D. in organic chemistry recommended adding 4-5 drops of pure household ammonia (without additives or perfumes) everyday for each 10 gallons of water. Ammonia concentration will quickly spike and then wane, usually by the end of the first week. As ammonia is converted, a nitrite spike closely follows. At that point, cut back to 2-3 drops of ammonia per 10 gallons per day until nitrites reach 0. This technique works great, producing robust bacterial colonies in biofilters in less than 2 weeks. [read
more
about the technique] Exercise caution: ammonia is deadly toxic to fish and amphibians; make sure it has been consumed completely before animals are added.
A more refined approach is to dose with ammonium chloride (NH4Cl), which gives finer control over concentration and eliminates the risk of introducing secondary toxins (perfumes, detergents) sometimes found in household ammonia. To dose 4 ppm N per day, add 0.58g NH4Cl for each 10 gallons of water. Again, follow the ammonia spike and wait for nitrites to wane before adding animals.
Biological media
Biofilters can use a number of different media to provide the requisite surface area for colonizing the beneficial bacteria. Undergravel filters use a rising column of air bubbles to draw water down through the gravel bed, which has a large surface area. Unfortunately, the gravel bed also acts as a mechanical filter, trapping detritus that will decompose in the gravel and block further water flow. The gravel must periodically be ‘vacuumed’ or otherwise stirred with a major water change. Alternatively, one could use a powerhead to pump water down the corner tubes and up through the gravel (reverse flow) to prevent such blockage. However, unless the gravel is the same depth throughout the tank, water will flow preferentially through the shallowest gravel – the path of least resistance – and only a small portion of the bed will be utilized as a biofilter. The sections of the bed with deep gravel receive very little flow and the water there can become devoid of oxygen. Such ‘anoxic’ water promotes the growth of anaerobic bacteria, which excrete toxins like hydrogen sulfide (swamp gas).
Sponge filters can also act as biofilters, again using rising air bubbles to draw water through the medium. A sponge has countless nooks and crannies and provides a large surface area for bacterial growth. Sponge filters are appropriate for smaller tanks with only a few, small animals. However, like the gravel bed, the sponge acts as a mechanical filter and can become clogged with detritus. It too must be cleaned periodically to remain effective. The trick is to rinse the sponge free of detritus without wiping out the bacterial colony. Usually, a couple of wringings under a warm stream of water will suffice. Remember to always keep the water level above the plastic air tube on the sponge filter or little water will flow through it.
For larger applications, one might want to use a trickle-type, a.k.a. wet/dry, filter. These units consist of various-sized housing containers, the size of which will depend on the bioload, e.g., 1 liter canisters for 20 gallon systems, a 55 gallon drum for a 500 gallon enclosure. The containers are filled with a biological medium and water from the tank is pumped to a spray bar or dispersing plate at the top of the housing container, where it then percolates down through the medium and back into the tank. Huge bacterial colonies then develop on the moistened medium. There are many types of biological media for use in trickle-filters – bio-beads, balls, stars, barrels, pads, ceramic rings, etc. – but all simply provide a large surface area for bacterial growth.
Fluidized bed filters
One of the most efficient biofilters is the fluidized bed filter. These compact filters utilize the same basic technology as an undergravel filter with several major improvements. A fluidized bed filter is usually in the form of a clear plastic tube 2-5 inches in diameter and 1-3 feet long, and hangs on the outside of the tank. A small pump feeds the filter, with a sponge prefilter to keep out detritus. Water is pumped from the tank to the base of the filter where it then rises up through a bed of sand, out a port at the top and back into the tank. The flow of water is just great enough to keep the sand suspended in the water column without blowing it out of the filter. This sand provides a huge surface area for bacterial growth, and because it is constantly suspended in the water (fluidized), there are no dead spots as with an undergravel filter. These filters are rapidly gaining in popularity and replacing the more conventional wet/dry trickle filters. The author has used
QuikSand®
fluidized bed filters for years with excellent results. The only downfall to using fluidized beds is that they deteriorate rapidly when water ceases to flow through them, e.g., during a power outage.
Do not confuse fluidized bed filters with sand filters; they both use sand, but that is where the similarities end. Water passes through a sand filter from the top down, compacting the sand bed, which acts as a dense mechanical filter to trap suspended detritus. They are decent mechanical filters but only marginal biological filters because they tend to clog and channelize. Fluidized bed filters flow from the bottom up. They provide absolutely no mechanical filtration, just a huge, easily accessible surface area for bacterial growth. They are excellent biofilters.
Maintaining the biofilter
Try to think of the biofilter as a living entity, which it in fact is. The bacteria must be supplied with a constant flow of warm, oxygenated water that contains low levels of ammonia and nitrite as food. They will suffocate and starve without this. It is a good idea to have an airstone or two in every tank and have the filter return water above the water surface to keep dissolved oxygen levels high. Allowing the return flow from a filter to cascade down onto the water surface or onto a rock pile can make for an attractive waterfall while aerating the water. If the tank must sit idle (without animals), move the biofilter to a tank with animals to keep it going, or simply feed it ammonia (see section above on cycling without fish) everyday. Also, be aware of the amount of time a biofilter is shut down during servicing. The longer it is down, the more bacteria suffocate and the less effective the filter will be until it recovers. Do not clean a biofilter excessively, just rinse the media if/when necessary, and NEVER use chemicals on a biofilter. Antibiotics can also kill a biofilter, so always treat sick animals in a separate ‘hospital’ tank.
It is a good idea to always keep a few extra biofilters going on tanks with heavy bioloads. That way, when a new tank is set up, a living biofilter is ready to transfer without having to wait for a new one to cycle. This is vital for that unexpected batch of tadpoles.
Combination filters
The most effective filters specialize in one type of filtration, but there are some decent ones that have different components in series. For example, some canister filters have different media in separate compartments. Water will first pass over filter floss or sponge to remove visible particulate matter, then over activated carbon to remove many chemical impurities. Finally, the clean water passes through the biological medium where ammonia and nitrite are consumed. Although more compact, series canister filters present the difficulty of accessing one medium without disturbing the others. In general, the Jack of all trades is master of none. The most effective filtration systems have separate components, at least one for each type of filtration. Moreover, one would not want to risk losing flow over the biological medium just because the mechanical medium became unexpectedly plugged with detritus.
Plants
Another often-overlooked form of filtration (bio and chemical) comes with the addition of living plants to the system. Plants help remove organic as well as inorganic waste from the water and are a great source of oxygen. Some aquarists use only living plants for filtration. Furthermore, plants greatly enhance the attractiveness of an aquarium and provide an oviposition site for many amphibians and fish. If the inhabitants of the tank are large or active and tear up rooted plants, try culturing the plants in a separate tank adjacent to the animal tank. Use the filters to pump water from one tank to the other. Just letting the tendrils of a potted plant, like pothos, dangle into a tank can significantly reduce nitrogenous wastes, especially nitrates.
Hi-tech toys
There are two other devices one might want to consider: UV sterilizers and ozone generators. UV sterilizers expose small amounts of tank water to intense ultraviolet light, thereby killing viruses, bacteria, fungi, and algae. The light is entirely contained within the sterilizer, which sits outside the tank, and poses no threat to the tank inhabitants. The key to its operation is that the water and micro-organisms must be exposed to the UV light for a significant amount of time, and this is controlled by the water flow rate through the sterilizer. Each unit comes with its own recommended maximum flow rate – exceed this and the unit will be useless. UV sterilizers are usually put inline somewhere after the mechanical filter, as suspended particulates can block the light from hitting the target organisms. Installing a valve on the mechanical filter’s outflow line will allow a small portion of its efflux to be directed into the sterilizer tube and the majority of flow back into the tank. Like all UV lights, these bulbs are relatively short-lived and need to be replaced periodically (usually every 6 months). Using a sterilizer for only a couple hours per day is all that is required in some cases and extends bulb life. The amount of time the sterilizer needs to be on will depend on the tank size, sterilizer power, and flow rate through the sterilizer. The sterilizer vendor should be able to help with these calculations as they relate to each individual system. It is recommended not to use a UV sterilizer on a new tank until the biofilter is established. Also keep in mind that sterilizers heat the water as would a heater of equal wattage.
Understand that UV only sterilizes the water exposed to it, not all the water in the tank. While the effluent might be sterile, the tankwater can still be teeming with microscopic organisms. A UV sterilizer does not kill everything in the tank, but by killing everything in the water passing through it, it helps keep microorganisms in check.
Ozone is a chemical compound containing three oxygen ions (O3). It chemically reacts with and destroys most organic molecules, pesticides, colors, and microorganisms in the tank. It provides complete water sterilization, but it can be a dangerous gas if not handled and vented correctly. Ozone generators force ozone into the water inline with the filtration system, and because ozone is a relatively unstable compound, it quickly reverts to molecular oxygen and so will not harm the animals.
Water changes
Regular water changes are essential to rid a system of the minor toxins that are not managed (like nitrates and phosphates), and to replenish any nutrients that were absorbed by the plants and animals. A minimum of 10-20% water changes every 1-2 weeks will generally suffice.
Summary
Remember this checklist for a healthy aquatic system: - Start with high quality water. - Filter the water three different ways: mechanically, chemically, and biologically. - Clean mechanical media at least weekly, replace chemical media regularly, and treat biological media as living organisms. - Do not overcrowd a tank: keep the bioload reasonable. - Do not overfeed the animals: uneaten food and excessive feces will foul the water. - Test the quality of the water regularly (at least ammonia and pH levels). Ask yourself, “Would I drink this water?” - Where possible, incorporate live plants. - Perform water changes often; if this is not possible or feasible, consider topping off with RO water to help maintain water chemistry in the interim.
Evaporating water leaves its dissolved contents behind, presumably concentrating the water in the tank. Replacing evaporated water with pure RO water would bring it back to its original concentration, but adding ‘whole’ water (reconstituted or tap water) seemingly would make it more concentrated with solutes (harder, saltier) with every top-off.
To test how significant the evaporation factor really was, I set up the following experiment. Three 5-gallon buckets were filled with tap water and churned with an airstone. When each had lost 1 gallon (20%) over time to evaporation, they got one of three 'water change' treatments.
Bucket 1 represents the’ quick-fix’ aquarist; the evaporated water was simply replaced with straight tap water and no water was changed.
Bucket 2 represents the ‘normal’ aquarist; after 1 gallon was lost, a second gallon was siphoned out and the two were replaced with straight tap.
Bucket 3 represents the ‘pedantic’ aquarist; the evaporated gallon was replaced by an RO gallon before a 1-gallon water change using straight tap.
'Concentration' was measured with a PinPoint conductivity meter. Measurements were taken 1 day after water changes, as conductivity rose significantly over the first 24 hrs. [I don't know why it would, perhaps dissolved gases have some effect, but it did stabilize after a day, so I took all measurements only after 24 hrs].
At the end of 3 months, solute concentration under treatment 1 had doubled, treatment 2 was up 43%, and treatment 3 was essentially unchanged (Figure D1). The practice of topping off with RO water clearly contributes to the maintenance of stable conditions. Note that this purist practice is not warranted in every or even most amphibian applications, such as enclosures with small water sections that can be changed 100%. Furthermore, most animals can clearly withstand large changes in conductivity. Consider the tadpole that begins life in a rain-filled pond and crawls out as a froglet after the pool has been reduced by evaporation to a puddle. However, the long-term effects of using whole water to top off in aquatic systems that receive small water changes can be substantial. It is just one more potential source of stress for animals already stressed by life in captivity, and it is easy enough to avoid.
Primarily aquatic systems experiencing high rates of evaporation or that receive only small water changes can be marked with “top” and “drop” lines, and regular water changes then consist of 3 stages. First, the tank is topped-off to the “top” line with pure RO water to make up for evaporation and bring concentrations back to preset values. Second, a given amount of tank water (usually 10-25%) is siphoned out to reach the “drop” line. Third, the level is brought back up to the “top” line using whole water. Some of the RO water added in the first step is indeed discarded, but the end result (consistent water quality) justifies the means. This is probably not as much an issue for the keeper of planted tanks, where presumably many of those extra ions are consumed by the growing plants.
