As far as fish go, the tank will be pretty used up due to the angel you have. You have to make sure the fish you have will have enough swimming room, territory, and growing room. A good rule of thumb to go by when buying fish is to find out what size tank they need, how large they will grow. They wont stop growing due to the size of the tank. Usually for each inch of fish you want to give 3 to 5 gallons of water. Otherwsie the fish can be stressed from being cramped. That can lead to disease.