1. Catfish sometimes require freshwater as juveniles and then as they get old they will need a more brackish environment. Make sure you read up on your catfish to learn what its needs will be when it gets older.
2. When keeping aggressive species of fish, it is best not to introduce peaceful species of fish among them. Aggressive fish will tend to bully the more peaceful fish. Make sure to thoroughly read about the compatibility of the selected fish for the aquarium.
3. You should always thoroughly research the type of aquarium you are going to be setting up before you purchase it. Make sure you have the proper gallon capacity and shape that will fit in your home.