I have a 125 gal fresh water tank. The residents of this tank is a 12 year old Oscar, 2, 4 year old Jack Dempsey's, 2, 4 year old glow fish, 2, 2 year old large Angelfish, and 2, 4 year old large Pleco suckers...My question is about my JD's, one of them is very large and aggressive while the...