1. Research the aquarium equipment you are looking at before you purchase it. Different sizes of aquariums require different pumps and heaters. Find out which products are best for your aquarium before you start ordering the wrong products.
2. 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.
3. Angelfish are normally very peaceful fish, in times of breeding they can get aggressive. It is a good idea to only keep one pair of mating angelfish in the same aquarium, as more of them can lead to infighting.