Lol, I should have added that I think he will be fine in a 20g. Some people only keep corys that reach 2 inches in 20g tall tanks, but I personally think a few of the bigger ones should be fine in a 20 tall as long as there are not too many other bottom dwelling tankmates.
I suggest you get about 3-4 of them. Yeah, they are pretty great little guys and they are even better when you have a few of them. You see a lot more behavior.