My girlfriends 5 year old daughter wants a red devil. I know that with my 75 gallon tank I have right now is stocked rather full right now so I know I can't add another fish like this to that tank. In the near future here we are moving and then I'll be setting up a 150 gallon tank. So what I'm thinking about doing is getting a 55 gallon cheap off craigslist to put a red devil that I can get from a guy I work with. what I'm wondering is would a 55 be large enough for a medium sized Red Devil. I'm guessing the one he has is maybe 6-7" in size. Later when I get the 150 set up I'd move him to the 75.