Wow, what a thread. How can you tell this guy that he is abusing his fish if he doesn't know any better either way. I've been seeing so much of these threads going on here lately. This site for the most part goes overboard on how to properly stock and filter a tank, and I know not everyone abides by what they preach. To the op, first, I'm sorry for all the flaming you got from all these know-it-alls, I'm sorry theyre perfect and know everything about fish keeping (although there are exceptions to every rule, everything from textbook doesn't always apply to real life). You came to the right place for info as there is still some good people left on here. My advice to anyone who wants to keep fish is 1. Figure out your tank size (which for you it's a 55g). 2. Figure out what type of fish you wish to keep. 3. Set up appropriate filtration for your stock. Since you would like to keep your JD, there are other species that can go along with it in that tank size and work. You'll have to do your research and find what you like. The task may be slightly harder since it looks to be the jack is fairly mature. Good luck!