I'm finally getting a couple of my tanks set back up after moving about a year ago. I used to breed fish but I don't have space for all the tanks now. I have my 75 set up and running now, started the fishless cycling process yesterday on it. I plan on putting one Oscar in there and calling it good. My boyfriend wants to set up the 55 long and is thinking about getting one big fish like me but isn't sure what to get. I plan on getting two penguin 200 bio filters for it. My question is what does everyone think we should get as the one big fish? I love black knife ghost fish but I think it would get too big even though some people say you can keep them in a 50. I was thinking about a flower horn as well but like I said I'm just not sure and would like some input. Thanks!