Instructions
Use a tank of sufficient size for the number of fish that you have. Overcrowding your tank with fish can result in low oxygen levels
Add underwater plants to your aquarium environment. This will produce excess oxygen for your fish, as well as help to keep things clean by serving as natural filters.
Clean out your filters regularly and remove any dead plants or other rotting material, as well as uneaten food. Also, remove any excess plant growth, since this can result (paradoxically) in lower oxygen levels.
Make sure that your aeration device is functioning properly and that your tank has good ventilation.
How to Improve Oxygen in Fish Tanks
If you have a fish tank at home or in your office, you know that there are a number of facets to creating a safe and healthy environment for your fish, such as making sure that you maintain the filtration system and clean the tank regularly. However,your fish's most immediate need is for oxygen. It is vital to make sure that oxygen levels are maintained at 5 to 7 mg per liter of water in the tank. There are several ways to accomplish this.