FW puffer for a 20 gallon?

[Born A Pisces]

I agree that active fish are better viewed in a larger aquarium. I have a cuban cichlid all to himself in a 60 gal and he's only 6 inches but still growing. He had a couple of convicts in there but he didn't tolerate them for long so I removed them. I simply don't have the room or funds for another tank. Looks like I'll go with an SAP or two. I was just trying to make sure I wouldn't be screwing over the puffer I bring home. Thanks for all the info. Much appreciated