SaxWHO?
Sweatervest has it right. Rays can be tuff to house correctly, as they require large tanks with lots of open surface area, which most folks can't provide easily.
Also, as mentioned, lionfishes come in several "flavors"...dwarf species, medium-bodied species, and large-bodies species. There are actually even coldwater species, both are dwarves, altho they're rather rare in the hobby.
Here's a good primer on lionfishes:
http://www.lionfishlair.com/careguides/lionfish.shtml
Altho I don't consider us "experts", my wife (Cranberry here on SWF) and I are kinda nuts for "things with stings", and we keep, or have kept several different species of
Scorpaeniformes, so feel free to ask any questions.
Thanks for the ind words, SV!