First and foremost, you really should let most Lysmata have a solid square foot of "turf" per scampi...er... shrimp.

The "Cleaner Shrimp" you speak of, I would imagine is Lysmata amboinensis. They are quite compatible with the peppermint shrimp (Lysmata wurdemani). The blood shrimp (Lysmata debelius) too is compatible with the others. So, unlike the issues you could have with a Coral Banded Shrimp (Stenopus hispidus), who typically do not tolerate other shrimp, you can rule out the "Battle of Scampi"

So, next.. the poor worms...You would have to have one heck of a bristle worm to tackle and consume your shrimp. We are talking about shrimp here; not a slug. If they feel threatened, they walk away. If they feel really, really threatened, they use their backsides and literally "high tail" it out of the danger zone.

Even after the photo period, with lazy tank inhabitants settling in for a nice night, I'd be surprised if a bristle worm would be able to take them out unless they were already sick and or dead. Finally, I'm just plain sick and tired of the neat detritus munching, sand stirring, worms getting a bad rap. Yes, a mondo-bristle-worm-from-h*ll can and will eat larger fare. The little ones...they are a benefit to your system.

So, lets move on.. I'm going to stick with the rest of the hobbyists and proclaim your gobids as innocent. They wouldn't take down shrimp. HOWEVER, many wrasse will consume shrimp, even larger ones. My 6-line LOVED ghost/feeder shrimp. He'd snap even the largest in half with his mighty snick and feed on the corpse thereafter. They don't have to be large wrasse to do this. However, my own 6-line, as a smallish/young fish NEVER harassed my cleaner shrimp. Not that it wouldn't when it was older, but as a younging, it stuck to small food stuffs.

Finally, there just MAY be a chance that your shrimp have molted and therefore have locked themselves into isolation until their new shells have hardened. This is quite common. DON'T go moving rock around to look for them. Again, if they've molted, they are quite susceptible to injury if bumped with the LR etc. Have you seen any molts floating around? You may not see them at all if the clean up crew has already taken them in.

In any case, give it a few days. Look around thereafter and see if you can spot them in the rock work. IF so, they probably molted. If not, the final conclusions could be that they were consumed by the wrasse, died and were consumed by the clean up crew (to include those oh so great bristle worms) or harassed to the point of jumping too! Check behind the tank.

Dave