I use it. It's vitamins for fish and corals basically. I do get a decent feeding response from corals when adding it to my coral "mush".
I add it to my coral food which consists of a chunk of LRS, a chunk of PE mysis, reef chili, and some selcon. Soak in tank water until the frozen is thawed, put in squirt bottle, float in tank until tank temp, squirt into corals and fish's mouths. lol
EDIT:
Forgot since I lost the fish, but I had a flame angel that was developing HLLE. This is when I first heard of selcon from reefers on here. Started adding it to the fish's diets, and it the HLLE stopped and most of it healed up so it was barely noticeable.