i always like paradise fish myself, they are a$$holes to everything in your tank, they chew on live plants, they will eat feeder fish, they WILL kick the crap out of all your other fish, if u have any. in a 30 gallon you could only keep one, unless you really want a show, buy a female to go with the male or vise versa, but thats cruel. there cousins to the siamese fighting fish, so they inherit the aggression, but paradise fish are much bigger, and get pretty big if kept in optimal conditions.