COBetta- The filter would be the same as what is in the 2.5Gal. We originally had it on this same 20Gal when we had a piranha in it. It's rated at 118GPH. The good thing is I know it won't suck the fish in with the sponge and plastic piece on it even on full flow.
sustina- We put new gravel in it that we are going to use with the terrarium. I rinsed it out too. Right now it's due for a water change in the 2.5Gal, and I didn't know how much I was going to do in the 20Gal, but I will do the 25-50 percent. Yeah, so far we have been pretty lucky.. with the terrarium, it is on hold anyways as I was debating filters and we had to wait for the frogs to get in stock where we want to buy them. So far so good though
Thanks for the info and quick responses. I will probably move everything later tonight.