Do your fish look tired, listless, not as colorful as they looked when you first put them in the tank? Something just seems wrong? An aquarium is a small world but it can suffer all the same problems of the big world. And pollution is the biggest problem you face.

Are there too many fish? Have you been feeding them too much? Is the water too acidic? Is the temperature too high? Or perhaps all of the above. The lucky thing is that you’re in charge and can make some quick changes that will set your little natural world back into balance.

Nitrite and Ammonia Pollution

If your fish are acting lethargic, nitrate and ammonia pollution are some of the first things to be concerned about. These two compounds are the major cause of aquarium fish becoming ill and dying. Both cause respiratory problems in fish but each in a different way. While ammonia damages a fish’s gills, nitrites stick to the fish’s red blood cells. Together, they deprive your fish of oxygen, make them anemic and leave them gasping at the surface. The stress that results makes the situation worse. While the problem may seem to occur overnight, it has most likely been building up over a long period of time.

Preventing Tank Pollution

When you set up your tank, and before you put any fish into it, give it a day’s rest or so to let the water rid itself of any dissolved gases.

Next, set up your filter and heater and let them run a day or two to get the tank in balance.

Test the water for both nitrites and ammonia to get a reading before you put fish in the tank. Ammonia levels should be within one to two parts per million in a freshwater tank, below one part per million in a saltwater tank. Nitrite levels should be around two parts per million.

Once you add fish, take regular readings to make certain a good level is maintained for your fish.

If your fish have a purple tinge to their gills, they are being damaged by ammonia. If they are shimmying and gasping at the surface, nitrites are most likely the problem. But since the levels of each are related, check both and make sure that the pH in the tank is at or below 7.0.

If Your Tank Becomes Polluted

The first thing to do is a major water change. Siphon at least half the water from the tank and replace it. This may put a dent in the concentrations of ammonia and nitrites, but only temporarily.

To decrease the toxic effects of the nitrites, if high levels are evident, add salt to the tank, a teaspoon to every gallon of water.

At this point it would be wise to reassess your little ecosystem. Ammonia and nitrite problems are not from new fish in the tank. They are maintenance problems. Are there too many fish? Five two-inch fish in a 10-gallon tank are plenty. Is the tank too warm or too cold for the kind of fish in it? Is the filter working properly? Has the filter material been changed regularly? Have you made weekly water replacement of a quarter of the tank? Once the nitrite and ammonia concentrations have dropped within range, the critical concern is good tank maintenance.