Things You'll Need
- Aquarium test kit
- Aquarium siphon
- Bucket
- Dechlorinated water
Instructions
Test the water using an aquarium test kit. Ideally, the level of nitrites and ammonia should be 0 or undetectable when fish are present.
Remove approximately 20 to 50 percent of the water if the nitrite and ammonia levels are too high and fish are already present. The amount of water you should remove depends on the readings. If it's higher than 4 parts per million, change 50 percent every day. If it's less than 1 part per million, change 20 percent of the water every other day.
Siphon the bottom of the tank using an aquarium siphon when removing the water. This will extract the decomposing matter trapped in the substrate, preventing it from raising the ammonia levels even more. Drain the siphon into a bucket, sink or bathtub.
Replace the water with either distilled water, reverse osmosis water or tap water that has been treated with a dechlorination agent.
Dose the tank with a product that converts toxic ammonia to ammonium after each water change. The nitrifying bacteria that consume ammonia can also consume ammonium, so these products don't interrupt the nitrogen cycle.
Do not change filter media all at once. Nitrifying bacteria live in the media, so removing the media can interrupt the cycle.
Monitor the ammonia and nitrite levels daily with your test kit.