Water Quality and Illness
High ammonia levels and other symptoms of poor water quality are common causes of illness in fish and invertebrates. Even if these conditions do not kill the animals outright, they stress the immune system and allow parasites and opportunistic microorganisms to establish themselves.
Ammonia is the most toxic of the nitrogenous compounds to be found in the aquarium, but high levels of nitrites and nitrates are also of concern. Invertebrates are, in general, extremely susceptible to ammonia and may perish rapidly when levels rise. Fish vary in their resistance to this toxin. High levels of ammonia will impair a fish's ability to transport oxygen to its cells, a symptom of which will be rapid respiration followed by listlessness.
A water change is the quickest and most effective way to deal with a spike in ammonia levels. Once this has been accomplished, it is critical that you identify the cause of the problem. An accumulation of uneaten food, a dead organism or a malfunctioning filter is usually behind a sudden increase in ammonia levels.
Nitrates and nitrites are less toxic than is ammonia but will also negatively affect the health of aquatic animals. Fish not immediately killed by high nitrate or nitrite levels will, nevertheless, suffer reduced growth rates and may exhibit labored breathing. Long-term exposure to high levels of any nitrogenous compound will also inhibit reproduction in most animals.
Chlorine, chloramine, and related chemicals are added by municipal authorities to our water supply to render it safe for drinking. They are, however, toxic to most freshwater and marine organisms. Both chlorine and chloramines may be removed instantly via the use of commercially available drops. Chlorine also evaporates from water that is left uncovered for 24 hours or so, especially if it is aerated.
Be aware, however, that chloramine detoxification may result in the formation of ammonia, which is toxic to fish and invertebrates. If you treat large quantities of water containing chloramine, be sure to filter the water through commercially available ammonia removing resins before using it in your aquarium.
Your local water authority should be able to provide you with the names of the chemicals that are added to your water.
Although heavy metals exist in natural bodies of freshwater and saltwater, they are extremely toxic, even in small amounts, in the aquarium. Copper is the heavy metal most commonly encountered by aquarists. Water that has passed through copper pipes, which today are most often found in older buildings, may pick up enough copper to kill fish and especially invertebrates.
Copper accumulates in water that has remained in the pipes for some time. If your water supply passes through copper pipes, you should allow the water to run for 15 minutes or so before using it. This will flush most of the copper from the system, but tests should be conducted until you are sure. You may also wish to consult your local water authority if you are experiencing an unexplained rise in copper levels, because many agencies use copper to control algae and parasites in reservoirs.
Certain rocks may contain heavy metals such as lead and aluminum. These may not cause problems in a natural environment but can, within the confines of an aquarium, poison your pets. Although live rock and gravel is often collected and used by aquarists, you may wish to be on the safe side and purchase these materials from reputable dealers.
Plastic plants that are placed in the aquarium must be designed specifically for use with living animals. Plastic plants, even flexible ones, may have internal metal supports that can rust if placed in either fresh or saltwater.
Fish and invertebrates poisoned by heavy metals may exhibit a wide variety of reactions, ranging from escape attempts to lethargy and increased respiration rates.
The use of aquarium medications must be considered in conjunction with other husbandry practices, because each change affects something else. For example, aquarium water containing safe levels of copper may be rendered toxic if copper based medications are introduced.
Many commonly used household products, such as air fresheners, glass cleaners, paints, and varnishes may be toxic to aquarium animals. Covering the aquarium may not necessarily exclude such materials, because fumes can be introduced into the water via the aquarium's air pump. If toxic chemicals must be used in the same room as your aquarium, be sure to cover the tank well and to disconnect any pumps that might introduce air into the water. Of course, the beneficial anaerobic bacteria in the filter will not survive long without oxygen, so it is best not to use toxic chemicals in close proximity to your aquarium.