A salinity rise can be more stressful on livestock than a drop. However, I feel like the rise would have to be kind of large like 1.020 to 1.025 to really stress animals out. I can’t remember why mine dropped its spines. Likely it was a high po4 issue. Mine had dropped all of its spines in a neglected tank and after some 30% water changes 3 days apart and back to regularly maintenance he completely recovered.I’m in the same boat my black long spine was doing ******* great up until two things happened
1) i raised my salinity level because i was adding corals
And
2) i added some crabs for algae control and they did too good of a job
so my little guy lost all his spines and he’s barely holding on
I think there is hope for you. It is just my opinion, but I believe that if you are able to remove him within 24 hours of death then all will be well. Change some water afterwards if there are concerns.
I like them and they do good work on algae. I have stopped keeping them because they are strong enough to drag my birds nests and digi’s as well as knock my frags off of rocks. It was a bummer to wake up and find a frag dropped in the middle of another colony and had been stung to death.