Hi, Im a rookie to fish keeping but seem to be doing pretty well. I have a couple of tanks but my largest is a 55 gallon tank with a 14' spotted gar and an 8' redtail catfish. The 2 fish seem to get along great and seem to be comfortable, however I want to add maybe 2 more fish. I need suggestions on what kind of fish I can add, and what size they need to be. I dont want to over crowd my tank already knowing the 2 fish i have are kind of large for a 55 gallon tank.