Avocado puffer behavior

[Eveebevy]

I’ve got an avocado puffer maybe like a month ago and he is not as active as I thought, from what I heard they are very active fish and are just always moving. But my little guy kind of stays in one spot and occasionally goes around the tank. Most of the time he is under a plant or piece of wood and he eats just fine. I don’t know what it is, I think maybe the tank is too small I read they need at least a 20 gallon, I really thought that he will need more space to swim back and forth rather than up and down and I have a mangrove tree that is still kind of small so I got a 24L x 11W x 7H. I thought that would be enough but maybe not he eats just fine I’m just worried because I know they are very active but he likes to swim around one spot under a leaf. What should I do? Should I get a bigger tank for him?

[Pufferpunk]

Mine lives in a 20g long tank. Hovers about 1/2 the timer