I don't know much about leather physiology, but when they grab on to food, don't they retract and pull it in? That could have been the response you were seeing. My duncans do that.
I dose 4 different feeds at about 1 tsp for 55gal (+sump).
I also have some hair algae but had it before...tank is still settling from setting up lol.
GFO will take care of phosphates but not nitrates if that is an issue. What sort of water changes are you doing?