lost sand sifting sea star

i haven't seen my star for a few days. do they moult? i'm experiencing a minor spike (i think) of nitrate although my ammonia and all other parms are good. i was wondering if it burrowedin and died somewhere?

 

I have 2 1/2 inch sand bed in a 75g and my sandsifting star will stay under sand for days at a time eating stuff then suddenly it surfaces and then goes under again

 

I will see mine about once every three weeks or so. If they are invisible it is a good sign. When they come out to eat.....that means the sandbed is too clean and it's looking for food.

 

thanks guys. actually it just now surfaced. i was reading up on seastars and i think i am going to have to augment his diet. any suggestions would be greatfully appreciated.

 

My Serpent Stars like small bits of silversides fish. They'll reach out from under a rock with one arm and pull the piece in.