The main problem with this fish are its food requirements. The issue is less the tank size for the fish, and more the tank size necessary for sustaining a good population of live pods, which it eats almost exclusively, hunting them off your live rock, glass, and sand. The reason tank sizes necessary can vary so much is that other factors control this than just tank size, LR/amount. Pod populations can vary and crash based on a lot of factors. Obviously the more LR and the larger the tank the larger and more stable your pod population will be. And a good refugium system can make up for a lack of tank size: it allows the pods to have a place safe from the predation of the fish so that they can successfully reproduce and spawn new populations.
But even so, this is a difficult fish to keep healthy and well fed. Because they are so pretty, they are very commonly purchased by people who really can't properly care or feed for them, which is really unfortunate.