Oh oh - fish MIA!

[snailbuddy]

Hi - it's me again with a new problem. Over the past few weeks I have fish disappearing - not a trace! MIA: bicolour psudochromus, scooter blenny, christmas wrasse, 2 cleaner shrimp and now I can't locate the bi-colour blenny! They haven't jumped out, no dead bodies, can't possibly hide that long - 50 gal tank. So, do I have an evil, unseen predator? Remaining fish are coral beauty, mandarin goby, yellowheaded sleeper goby, 2 cleaner shrimp. Have assorted corals: fox, candy cane, colt, various zoos, various xenias, various mushrooms, sun coral, coco worm, feather dusters, snails, & 1 small emerald crab which I haven't seen for a while. I have heard several loud snapping noises . . . could it be that there is a mantis shrimp in the tank? I've never seen anything like that at any time of the day or night, but I know they can hide well. Any suggestions would be welcome.