I guess I just wouldn't use the term "specialized" While he is in a custom tank there is nothing "special" about it. He could be kept with corals, I just don't bother since I have a reef a few feet away. I used to keep some softies in the tank but not anymore.
Fed a couple more fiddlers today. I've had them for months and months so I should burn through them before they die. The filter on their tank died and I don't plan on replacing it, however the small amount of water is still clear and does not smell. There's probably another aquaclear in my basement somewhere I should check...
I don't put the lid on the jar one because i think it's made of copper and two I'm not sure if he would be able to get it off. He has been hesitant at times to go in the jar and prefers to reach in and pull the crab out.