Please Help Asap

Hi Everyone
I bought a pink tipped aneome last weekend (Sat.).. it was fine all week Did a 15% water change on tues. night. thursday night he moved to the back of the tank.. by a rock.. friday kinda went under the rock so i couldn't feed him.. and yesterday i couldn't get to him to feed him ( pet store gave me mysis shrimp/( frozen) which i have been thawing and feeding by eye dropper.. )this morning he seemed fine and then tonight when i got home. i couldn't see him at first and then i noticed this dark mass on the bottom of the tank.. it is the aneome and he is dark in color and all sirvaled up.. Should i remove him or do they sometimes does this. i know if they are decomposiong they will release unwanted toxins in to the tank and i would like to prevent this .. \
all help wpould be greatly appreciated..\

The thing is though that he was eating He tried pellet food at first but spit that bad up and was eating the mysis shrimp no problem i noticed that night he came back to normal after a couple or hours and he did the same thing last night.. I have been topping off with tap water every 2 days about 2 gallons of water.. and cleaning the scimmer every night, i notice as soon as i top off the scimmer is full with almost clear water.. and i am having a break out of white circular creatures really smalle nm in diater.. look like little worms curled up on the walls of hte overflows. and my white tube worms in the sump are getting big. one has actually managed to get under my mag 12 pump in the sump and angle the end up.. Wondering if maybe i should move this one..?
i am b