Partial Water Changes
About every other week you should do a partial water change. This will all depend upon how many fish you have in your aquarium and if you have an unusual amount of Nitrates (see the page on The Nitrogen Cycle) when you test for them. After you have been "fish-keeping" for a while, you will just plain know how often to do this and how much. Usually, the first couple of times you should change about one-third (thats not quite half) of your water.
Remember, you NEVER take water straight from the faucet to put in your tank. You should have water sitting in containers somewhere and it should have been sitting for at least three days. Before you put the water in your aquarium, test it for Chlorine. Your Chlorine level should be at "0".
Check your filter for dirt and if it needs cleaned (better get an adult to help with this), clean it in the water you have just taken out of the tank before you throw it away.
After you have poured in the new water, do testing for ammonia, nitrites and nitrates and pH. After you have made sure everything is within safe levels, just plain enjoy your fish!
