New ACF not eating

[Geoff]

I got him three days ago, and I'm sure he's getting hungry. It isn't urgent yet since he's fairly big.........

Also, he's been making mating calls I can take that as a compliment, right?

In my opinion there was no problem here. You acquired a large, healthy adult frog in breeding condition, which was more interested in breeding than eating. The sudden change in his environment probably triggered the calling. If he's been well fed previously he'll have sufficient reserves to last him for many months without food. Also, these frogs do occasionally go through phases of not eating, which is nothing to be concerned about.

I've been doing daily water changes (1-2 gallons)

I don't understand what useful purpose the daily water changes serve if the frog isn't producing any waste. If you get a filter please bear in mind that these frogs, unlike many fish, do not inhabit, and have not evolved to exist in, fast flowing waters so it's important not to subject it to a constant whirlpool.