MY SPIN ON BLUE LINKIAS
You need to acclimate them for hours. I usually acclimate one for at least six.
I've managed to keep them for a few years. I don't know about the sponge thing (I have lots of sponges*) - I'm more likely to agree with the belief that they graze on "bio-slime". (I wish they would graze on hydroids.)
Orange Linkias are not as fragile as Blue Linkias. I can't speak for Purple Linkias - I've never owned one and I rarely see them. And when I do see one, it has been quite large.
There was a theory going around several years ago that Blue Linkias would melt down if they were handled with bare human hands - something about amino acids on your skin. I don't believe there were ever any studies done on it - but I like it when I see someone taking one out of a system with a plastic bag on their hand.
If a Blue Linkia is going to melt down, it will usually do so within 7 to 10 days of being introduced into a retailer's system. So, if you want one, only buy it from a retailer who has had it in their system for longer than that (the longer the better). Needless to say, don't buy one on-line - you have no idea if they got it in yesterday or a month ago.
FWIW, I will only buy a Blue Linkia from one retailer in my area (NNJ). They've been in business going on 40 years, and they know who they can safely buy Blue Linkias from, and who they should avoid. And, when I ask how long they've had one in their shop, I trust their answer.
* One of the best comments I've had on my show tank was from a science teacher in NYC who I was selling a group of Poison Dart Frogs to. He was setting up a vivarium in his classroom. He was actually impressed with the diversity of sponges I had in my tank. It turns out that he was spending his summers in Panama working on his PHD in sponge taxonomy. None of the sponges he saw were purchased by me - they were all from live rock I had purchased from many sources many years ago.