I nam taking down a twenty gallon fw aquarium( I'ver been bitten by the marine bug).I would like to make it a FO marine aquarium.I will have an H.O.T magnum filter,and possibly a skimmer.I am interested in venomous fish or something very predatory.It doesnt have to be very active.I would also like something rthat doesnt jump(alot).Any suggestions would be helpful.Thanx