Here are my suggestions:
gulper catfish or a couple fancy oranda goldfish not sure what else to say all things that came across my mind were cichlids lol
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You could fit seven goldfish in there. Maybe each one a different kind? Or seven of the same type just different colors? I happen to love ranchus and ryukins. eastcoastranchus.com has some VERY good product and worth every penny. Just remember to take your time in ordering them so you are completely content with your selections. If your going to pay between 45 and 100 dollars per fish you should get something that screams "TAKE ME HOME!!!". I ordered mine over a several year period of time. The ones with the most interesting patterns come along infrequently and are quickly snapped up. The ranchus are very fascinating to watch swim since they "wiggle" as they have no dorsal fin. They also seem to be full of personality and intelligence. I have one that likes to be touched. Be sure not to get ones where the wen is growing over there eyes. You will just end up having to do minor wen surgery. I have to do that to two of mine. Not really any big deal but cutting on my goldfish still creeps me out. raingarden.us has some very nice yellow goldfish. Dandyorandas.com has a nice variety. I would not buy their orandas though.
Best of luck with your new tank. Remember goldfish are hardy, require no heat and have many different kinds and variations to choose from. Goldfish are just the best!!!