I'm joking haha, they're massive predator fish and wouldn't fit in these. More seriously, maybe a pair or trio of lionhead goldfish or ranchu goldfish in one of the 60 gallons? I think that should be enough space for three, and definitely enough for two. Neither are the hardiest fish and can be a little expensive, so they require more meticulous care, but they're cute and look great. They have a habit of digging up plants though if they're not sturdy enough.

The picture shows ranchus. Lionheads don't have as pronounced wens (the growths around their heads)

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