Miles is right about there personallity being very similar to a puffers. That constant loomy dance they do just before darting for there prey is awesome.
They get 12-13" from every information that I have read on them. I would imagine a 75g+ should do the trick.. Giving them atleast 6 inches of turnspace. They enjoy some floating plants to 'linger' under.. BGG has a small school of 5 of them, and I think they are still doing well.. They would be fine in a 55g until they got larger!
This is actually two sp I have found. one has a red tail and spots. (second picture bottom left) the other has a line and the dorsal and adipose fin are farther up on the body (second pic right)