Copodes or not

I recently lost my third set of bullet gobies a red and white firefish and a manderin(never found any bodies) did notice the gobies gettin thinner local LFS said they are starving however I have watchman,clown,pinkspot gobies all doing well and one scooter blenny all have been in tank 6+ months and ive never seen any of them eat what im feeding the take which is nori and mostly all ocean nutrition frozen and dried food plz help whats going on since not reef and no fuge should i still add copodes

 

First how old is your tank. You should not attempt a mandarin unless its a very very established tank with a huge pod population. Scooter blennys will sometimes eat other stuff even though you dont see it. I would put a pile of small rubble in your tank and try to get some pods in there. They should live and multiply in there.