They really aren’t that hard to keep. The red and purple ones tend to be heartier than the green ones in my experience, and aquaculture ones tend to be heartier than wild caught. ORA sells aquaculture ones that people keep with great success, see those do the best long term.
I target feed mine daily with Reef Roids, and they grow more quickly with that than broadcast feed or not feeding. They like low to moderate flow with a random component. The tentacles should move without banging all over the place, if they do then the flow is too high. They aren’t as fussy about light, but will start to bleach if it’s too high.
They come in lots of different colors, we added a blue one and yellow/pink one a few weeks ago.
Good luck!!