If its a pistol shrimp if you put lots of live food in with the lights out you can hear them feed. They dont make noises too often. If it is a clear clicking sound it is possible. I found one in my old six foot tank when i found a round hole in the rock that had tiny chip marks around it where he had been making it bigger. It was about an inch long and clear except three very light brown rings around it. to be honest i put him back in.
I have never had any problems directly caused by bristle worms to be honest. Most the time when people think that they have damaged somethinging it is already dead or dying. Bristle worms are exceptionaly hard to get rid of the best you can hope for is managing there population. Arrow head crabs eat them but are a pain in the #OOPS# as they also eat fan worms. The best way to limit there population is to minimise there food by not overfeeding your other stock.
you can use a sheet of plain papper to clean up the algae place it on top and it will suck up the algae and it is probably caused when you have water changes make sure that you test the water you are putting into the tank even if its r.o as the membrains dont last forever.
its worth moveing corals if they dont seem to be getting on. Sometime better light or flow can pick them up in no time. Also even if it seems completely dead clean the rock off and put it back in the tank and sometimes they will start to come back from the smallest of pieces.
Most puffer fish are pretty bad swimmers and dont always like a direct current in the tank you may find that you need to direct the power head at rocks or the glass but when you get one in there see how it goes. I always found that algae blennys were a bit fussy with food if they are given plenty of algae to eat its not a problem.