All living creatures give off waste, fish are no exception. These waste products which are nitrogen base break down into ammonia, which naturally is highly toxic, to just about all fish. In the wild, the volume of water per fish is very high in waste products become diluted to very low concentrations. In your aquarium, however, it can take as little as a few hours for the ammonia concentrations to reach toxic levels.

So you may be asking yourself how much ammonia is too much. Well, if you have a test kit for ammonia and test your water, and you’re able to measure the ammonia in it then you have too much. At that point you may want to consider doing a water change to get the ammonia levels down. But as in nature, there are ways that you can keep the ammonia level under control in your aquarium.

Aquarium nitrogen cycle


In your aquarium, the nitrogen cycle is the biological process that converts ammonia into relatively harmless nitrogen compounds. Several species of bacteria do this work for us. Therefore, when you hear the term -cycling the tank- this refers to the process of establishing bacterial colonies in the filter bed or gravel bed that convert ammonia into nitrates.

Now establishing the desired bacterial colony is not as hard as you may think. The nitrifying bacteria are present everywhere, so as soon as you have ammonia source in your tank is only a matter of time before the bacteria will establish a colony in your filter bed or in your gravel bed. Easiest way to do this is when you first set your tank out, place one or two inexpensive fish in your aquarium. Their wastes will produce the ammonia that the bacteria will need to feed on.

What you’ll noticed when starting a cycling process is the ammonia levels will go up and then suddenly drop down as a nitrate forming bacteria do their job. Once the bacteria take hold, nitrite levels will fall and nitrate levels will rise. Once this happens, the cycling process is complete.

You will need to buy the proper test kits. To determine when the cycle has completed. The process can normally take anywhere from two to six weeks. You will know when you’re aquarium is fully cycled and when the ammonia and nitrite levels are zero, and you are seeing levels of nitrates.

So that your aquarium has cycled, what next. Well now, is it time to slowly add fish to your aquarium. It is recommended that you add no more than two fish at a time to your aquarium. And allow sufficient time between the adding fish for the bacteria level to adjust to control the ammonia. This will eliminate a sudden rise in the fish waste and naturally, a sudden rise in ammonia.

What is a balanced aquarium?

Originally the concept of a balanced aquarium was that the standing aquarium is a self-contained microcosm – a little world. The theory ran that as the plants manufactured food through the process of photosynthesis; they utilized carbon dioxide and gave off oxygen. Fishes, on the other hand, gave off carbon dioxide and utilized oxygen. Fishes waste, according to the theory, fertilized the plants, while excess plant growth provided food for the fishes. One thing thus balanced another, and no outside care was required.

Unfortunately this theory simply does not hold up in practice. While plants do give off oxygen in excess of what they use for respiration, they do so only in the presence of bright light. When the aquarium is dark, they use up oxygen just as do the fishes. Water cannot store more oxygen than the amount required to keep it in equilibrium with the air above it. Excess oxygen passes off readily. The same does not hold true of carbon dioxide. It tends to stratify, forming layers along the bottom. (Circulation prevents this stratification.) Having a maximum air surface in proportion to the depth thus goes a long way toward keeping the aquarium properly balanced.

The waste matter produced by the fish is far in excess of the amount required by the plants. Moreover, most of our aquarium fishes are carnivorous, eating animal, not vegetable, matter. Even the more herbivorous species require some animal food.

So the idea of a balanced aquarium is a fallacy in its original concept. An aquarium in balance is, however, what can be achieved.

The factors that modify an aquarium more or less balance each other includes the proper amount of light (too much over stimulates algae, too little does not permit plant growth); the proper amount of food (too little stunts the fishes, too much pollutes the aquarium); the proper number of fishes; the correct size of aquarium, and the proper temperature, etc. All of these things must be in proper balance with respect to themselves and the others if the aquarium is to flourish.