1. Pay close attention to your fish's PH needs and augment your aquarium as necessary to accommodate the new fish you are adding to your aquarium.
2. You should feed your fish a variety of food and not just flake foods. Mix it up with fresher foods from their regular diet. Giving them more a varied diet will increase the general health of your fish.
3. In larger aquariums, you should put a few scavenger fish in the tank. Scavenger fish will help to clean up left behind food and wastes from the other fish in the aquarium. This is a good eco friendly way to keep your aquarium clean.