Now that you have your tank set up and your fish are doing well, you still have a job to do. We need a way to remove the buildup of nitrites and other excreted pollutants that can make your fish sick, and possibly kill them. In nature, water changes are performed on a regular basis when water from streams and rivers flows into a lake and back out again. In a closed environment like an aquarium, we need to perform the water change ourselves.

Water changes are not a big deal if you are prepared. Here is what you will need:
A siphon hose 3 to 5 feet long.
A 3 gallon bucket.
Water de-chlorination drops.

A good rule of thumb is to replace 20% (one fifth) of the water every two weeks. Here’s how to do it:
Place the bucket on the floor next to the tank.
Place one end of the hose in the tank water.
Suck on the other end of the hose to begin syphoning the water from the tank into the bucket (siphoning may take some practice, no, the water is not harmful if swallowed, just unpleasant). You can purchase a small pump if you would like to avoid using your mouth.
When the bucket is full, take the hose out of the bucket and raise it above the level of the tank water to stop the siphoning. Pour the fish tank water over your lawn or flower garden (the water makes great fertilizer).

Repeat the process until you have emptied 20% of the tank. For example, for a 10 gallon tank, you need to empty 2 gallons of water.
To refill the tank, grab a bucket and your de-chlorinating drops. Make sure you rinse the bucket well before using. Fill the bucket with fresh tap water and add de-chlorinating drops according to the manufacturer’s instructions. You may want to wait until the water in your bucket reaches room temperature before you add it to the tank, especially if it is really cold. After you finish adding the treated water, you are finished!