And they need pretty large tanks(6' tall was something I remember hearing, that may have been for a proper spawning rise though), which means equally large equipment to keep up with the water volume and potential bioload of all the food you put in.
And even with a perfect setup, you may not be able to find one, and if you do and can't keep up with its nutritional needs then it will starve, maybe slowly, maybe quickly. Either way, not something you want happening to a $500 fish. IMHO, seahorses are just as cool, and much more doable. H.ingens is a larger(and more elegant, IMO) species than the more common erectus, barbouri, reidi, and would make an excellent species for a larger display.