I have two leathers, the devils hand and a little yellow one (unidentified). The devil was in the tank for at least a week before it opened the fingers and now almost always does. The other one opens the fingers some days and not on other days. I think this is alot like the pervasive quesstion of why a bubble tip anenomes sometimes does and sometimes does not bubble its tips. Thier is no "one" answer imo instead it's more likley a complex combination of factors, lighting, water quality, feeding ect.