I got him from my LFS and was already missing part of one arm, but over the last two weeks lost one entirely. I read that means he's not getting enough to eat. My aquarium is two months old but there's plenty of detritus for him to munch on. He recently found the part of my tank where the flow isn't great stuff builds up so I'm hoping things turn around. Are there any kinds of supplements I could add to help him out?