The more I observe the pair of WTF the more I think that for them to be at least content is a 40 gallon. I have them in a 30 and had them in a 18x18x24 and they just seem a little cramped. A 40 gallon is enough floor space and height. These frogs will use the whole tank, they are not always up on top of plants. Mine come down to the water at least half the night. When I am recommending to people about a WTF I am going to say at least a 40. They get 4-5 inches which would mean they would be miserable in a 20 gallon. I'm not trying to downplay anybody who keeps them, I'm just sharing my opinion. If it's a 20 gallon maybe a terrestrial species would work.
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