• Water Changes

Water changes should be done on a regular schedule. How often depends on how many fish are in the tank, how much they are fed, and the size of the tank. Again, a larger tank allows more room for error with water changes. In most cases, the more often the water is changed, the better. A conservative standard would be once per week. Test kits can be used to actually measure the amount of ammonia, nitrite and nitrate in the aquarium. This may be important for a new tank as the bacteria are getting established. If you don't want to buy a test kit, a good local aquarium store will test the water for you if you bring them a sample in a clean jar. If you're not sure whether a water change is needed, go ahead and do it. Clean water is healthier for your fish than dirty water.

Even if you have plenty of filtration and happy bacteria, this is not a long term solution to eliminating fish waste. The ammonia-eating bacteria are perfect for eliminating the highly toxic ammonia that can quickly kill your fish. But the nitrogen from this ammonia is still in your aquarium. You may hear reference to "the nitrogen cycle". This refers to the various chemical forms that nitrogen from fish waste takes as it is processed by microorganisms in the tank. This process is certainly very complex. But in simple terms, ammonia from the fish is converted to nitrite, and this nitrite is converted to nitrate. A healthy bacterial colony will change all of the nitrite to nitrate. This is important because nitrite is also very toxic to fish. As long as the bacteria can turn the nitrogen into nitrate, your fish are safe for the time being. But over a long period of time the nitrate will accumulate in the aquarium and cause stress for the fish. Some fish are very tolerant of nitrate and others are not. That's why water changes are necessary. The best way to remove nitrate from the aquarium is to remove the contaminated water and replace it with clean water.

Certain types of fish may also be sensitive to the pH and hardness of the water. Check with your supplier about this.