It depends on what you put in it, and who is cleaning it. Assuming that you have the appropriate number and size of fish/reptile/whatever, 10-15 gallons is average for most households. If your nephew is responsible for cleaning the tank himself, and is a kid or young teen, 10 gallons is about as large as i would go until he proves he can take good care of it.
answered 1 year, 6 months ago
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