My 180g reef is losing hermit crabs daily. I had 30ish blue and red leg crabs and now all I see are shells? Water parameters are good. Fish, snails, and coral all look good. I feed heavy for the amount of livestock I have and use a good variety of foods. Whats happening? Could something be eating them?
My livestack is pretty normal. 1 six line, 1 bird wrasse, 2 tangs, 1 hawkfish, 1 manderin.

If the shells are cracked you could have a mantis shrimp.

Sorry about your loss, that sucks.

How long have the hermit crabs been in your system, are they new additions or have they all been around a long time? Have they been properly acclimated to the tank?
Mixed species? Plenty of extra empty shells for them to trade off during growth?
Absolutely the animal itself is dead and it isn't a molt? Any visible attacks from anything including a hidden mantis shrimp would likely leave injuries/cracked shells. It could be a hermit crab disease of some sort being passed around that you really can't do anything about.

If it were me I would not add or replace any hermits in the near future, continue to care for my system as normal watching all the other inhabitants closely. It might be better to do without them in your system for awhile. Better to not have any hermit crabs at all than to risk losing other creatures due to changes you might inflict while trying to find a solution. Maybe the cause will become apparent later.

I have a huge coral banded, but no sign of a mantis shrimp. shells appear to be intact. Most crabs are about 1 month old. At the same time I added ones to my 29g nano and they are doing fine. I think the advise to wait a while to replace them is valid. Thanks.

What would a mantis shrimp look like? Is it something i could easily see?

Do a Google search for mantis shrimp.

I don't believe you have a mantis. I keep one in his own tank and have noticed that he likes to decorate his home with his kills. Talking with other people on RC who have them, it seems that about 90% of them do, so if your empty shells are simply scattered around (and not cracked, as the previous posters mentioned), my bets are it isn't a mantis.

When hermit crabs begin to outgrow their shells, they kill other hermits or snails (ceriths seem to be the favorite) and rob them of their shells. You can go to your closet pet store and probably buy empty shells for extremely cheap. Toss them in the back of the tank, and maybe the murder will stop. lol

If I'm wrong and it does happen to be a mantis and if you're able to catch it, please don't kill it. I have a tank set up and ready for another, I just haven't gotten the money to order one yet. I'll gladly take it rather than it be killed. But I don't think it's a mantis, still. lol

I have no signs of a mantis, but ALL of my crabs seem to be dead. The turbo snails are fine and the hermits in my nano are still fine. My coral banded shrimp is huge and very active. I still think hes the bastard doing it but I haven't heard of them killing crabs before. For now I guess I'm going to delete crabs from my clean up crew. What would you suggest to go with my turbo snails that won't turn over my rock or get eaten?

Jay Shelton

180g reef
29g nano

How about a sea cucumber? I love mine -- he doesn't bother anything and nothing bothers it. He eats the sand and poops it out cleaned!

thanks. will give it a try. Are they pretty easy to keep? anything in particular i should know?

I've had mine for 10 months now and it hasn't required any special care or feeding beyond keeping a stable tank.