I had a pair of jewels once, and they ruled half of a 75 gal. tank. A buddy was looking for a tank mate that might could hang with his RD. we all know how cranky a RD can get. So i told him he could have the jewels as long as he rearranged his tank to try to shake up the RD and then slip the jewels in. He has had them for right at a year now and all is well. (Just Saying)