I wouldn't take him out yet, I had one do a 360 after making sure it swallowed a big chunk of shrimp and calibrating my refractometer. I was running salinity at 1.010 before I calibrated!
I was feeding reef roids and mysis but never really saw it eat. Also crabs would get in there and steal food
I would put it in an acclimation bin in your tank and give it an eraser size piece
Yes this happened with mine with shrimp & fish. You need to put it in an acclimation bin in your tank and get a nice eraser size chunk of shrimp that you cut triangular shape and place it on its mouth. You will see it start opening its mouth trying to eat after a few minutes. Since it doesn't have its tentacles to pull food into its mouth you have to get some tweezer and carefully push the pointed corner of the shrimp actually into its mouth so it can get ahold of it. It's a pain in the butt but it saved mine! I'm sure it was starving. Make sure to thaw the shrimp in a little side dish of tank water before feeding. Post updates after you get the guy fed please.
