40 gal should do just fine. Rule of thumb is 10 gal/frog but more is always appreciated. For a filer most recommend a whisper filter or something that doesn't create to much of a disturbance as these guys can sense vibrations in the water and too much going on can potentially stress them out.

For food you can also feed blood worms, or basically any pelleted aquatic turtle/frog food that is small enough to fit into their mouths. A lot of people recommend reptomin sticks, you can break them up into bite size pieces. For hand feeding nightcrawlers are great, again you can cut these into bite size pieces. But as they grow they can handle longer and longer worms, it's pretty funny to watch an adult eat a whole nightcrawler.

I've heard these frogs recover from injuries very well. If he stops eating and acts lethargic then you may want to schedule a trip to a vet. So him swimming around and eating are both good signs. Keep an eye on him. A weak frog could turn into a meal for a slightly bigger tank mate.

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