**Update** Now Dying

Mine was getting skinny until I switched to Hikari Multi-Vitamin Enriched Krill. I would also soak some in selcon. He lived a fairly long life after that, and was fat and happy until he died when he got stuck in the overflow.

I think the texture and size of the food is important. I would grind it up first. I did find though certain foods for some reason, although he would eat them, would pass right through his gills. I think their gills are adapted to catch certain types of food. If it is the wrong size or texture, it passes through and they don't get the nutrition. Parasites could also be an issue although for mine that did not seem to be the cause.

 

It looks like his face is getting red. I've never had any marine pet survive after getting that red tint around the mouth. I'm sorry for you an your little guy

 

My 6-spot will send whatever he doesn't like out through his gills. If he likes it, he eats it. I've seen him accidentally send a piece out through his gills, then turn around and eat it. I think it's an entirely voluntary thing.

 

Try giving him sum milk

 

milk?

 

I still say you definately need to treat him for an internal parasite

 

I had the same issue with mine in a previous tank his appetite decreased and a guy at the LFS recommended a skunk cleaner shrimp and he started to get better at eating. Mine was not at this stage that yours is now though. Best of luck on a recovery.