Have you looked into catfish? Plenty stay small enough for a 37. Madtoms, for example.
Or you could get a big mean CAE and watch it spaz out all day the way they always do. Thoroughly good entertainment, CAE's are.
ive always wanted like 1 large fish like idk a large sen or del or somethin like a community fish. basiclly either a large fish or a lot of small ones
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The problem is you can't have a big fish with a little tank(think Tommy Boy - fat guy in a little coat). If there isn't one fish that you really want you might be happier with a busier community tank.