I have Geo's in with my retics. They do great together. Try and stick with a calmer species. I wouldn't do Red Zebra's, they are african cichlids and very aggressive. Wouldn't do kribs either. They'll get eaten, no matter how many hiding spots you have. Steer clear of the snook. You want something peaceful, that grows 6" or so. Severems, Geo's, Uaru. In a 125 you could do a group of 6-8 geo's and they rays. You don't like discus... how about angels? There a a lot of options for tankmates, but like I said before, they can't be aggressive.