sand sifter blenny/goby starving

hi guys idk witch it is goby or blenny but hes a sand sifter with blue spots on the side of his head and bodys white. he ate all the algae on my sand bed in my 55 gal and his belly is so thin his rib cage and all is showing idk what to do hes all sucked in horibble looking i got this stuff called reef plankton its little orange cubes the fish store sed he woad eat it but he isnt at all he picks at brine shrimp but not near anuff any suggestions on what i can feed him?

 

Sounds like a gold headed sleeper.
They rarely accept prepared food. They need large tanks with a large sand bed and attached populated refugium. Sounds like a case that could have been avoided with research :-/

 

i have a refugium just that i dont have any plants and stuff in it i leve my light on from 10:00am to 8:00 pm so i tho tah twoad grow lots of algae for him. im gonna gets soem live and and cheato grass

 

is it a gold sleeper or a diamond goby? from the colors you gave it sounds like a diamond goby..but anyways what are you trying to feed it?? mine really like chopped squid..