A full sized panther grouper will be able to eat an angler i believe. Make sure you get the angler full sized, and the panther grouper as a juvy, but not small enough to fit in the anglers mouth. Just to let you know, anglers are best left to species only tanks cuz of their incompaitbility. They will either eat their tankmates, or their tankmates can eat them. Its a tough predicament, but if u insist, then i guess you can see how it goes. Id think it better to not put a grouper in with it, cuz it might try to eat the angler. But triggers, puffers and probably lions will be allright, groupers are just next on the list for the big mouth thing is all