Hermits and snails disappearing

[dbacksrat]

My tank has been running for about 18 months now, and over that period I've added at least 45 blue legged hermits and dozens of snails (turbo, astrea, trochus, nassarius, etc). Why so many? Because they keep disappearing. Somehow, they are being picked off, one by one. There are 5-8 cerith snails (small) and one hermit left. This hermit has been the ultimate survivor for months now. There used to be a large oddball hermit that was three times the size of the others--he recently turned up dead.
I know hermits have a short lifespan, but at least 45 dead? Do I have bad luck, or is something else happening here?
All of parameters are in the acceptable range--the only thing thats a bit off is NO3 @ 10ppm (which shouldn't be a problem, right?). My meager handful or corals look great, and there are various macroalgaes that are starting to take off (grape caulerpa and a bit of halimeda, both hitchhikers). Because everything looks fine from a visual point of view, I doubt there is anything chemically killing my inverts.
Here's another clue: right after the lights go out at night, I hear a popping noise. Maybe a shrimp of some sort? I don't want to jump to any conclusions, but I want to get to the bottom of this because I cannot keep any crabs or snails alive in this tank. Any ideas anybody? Thank you for reading through this.

 

[wayne]

Well I have the same problem as I have a 'naughty' hermit. He's a very large blue leg, and he jsut slowly goes thro' the others.

 

[Limi310]

Popping noise make me think of a Mantis Shrimp.

 

[ram man]

are they disapearing shell and all? is you can find the shell of a dead hermit that has a whole in it and take a pics i can let you know if a mantis killed them. popping is usualy the sign of a pistol shrimp not a mantis, a mantis is more of a click.

 

[dbacksrat]

All i find is empty snail shells, and no empty hermits. I have not seen any kind of shrimp--I just saw how small a pistol shrimp can be at my LFS, so a pistol (if existant) could be anywhere in my 29.
I'm thinking maybe I could bait some sort of trap and see what I catch--any other better ideas?

 

[ram man]

a trap would be the best thing, if it is a mantis you can trade it in to aquatouch for around 40 bucks.

 

[dbacksrat]

I was hoping it was a pistol--but if its a mantis, $40 would be great.

 

[ram man]

if it is a mantis could you post pics? try the inverted bottle trap, just take a empty washed out soda bottle and cut the top of, then put it in the bottle upside down and make sure the is plenty of room for what ever gets in to stay in, put a piece of food in and see what happens.

 

[sparker]

the bottle trick that ram man suggested is what worked for me, my tank was up and running for about 6-8 months before i noticed that i had a mantis shrimp. and ram man is right about the clicking rather than a popping.

 

[dbacksrat]

Ok i'm gonna try that tonite--its making me crazy not knowing what is going in my tank. We'll see.

 

[dbacksrat]

Night 1: I baited the bottle with a piece of squid...all I caught was a Nassarius snail (believed to be dead). I guess thats some good news. I will try again tonight.

 

[RockingCricket]

Found thjis thread while looking for some info on Halimeda. Did you find the culprit in the end Dbacks?

 

[dbacksrat]

Nope...I still hear clicking at night though. There are now an urchin and an emerald crab that have been thriving in there for a month. I also just added about 30 snails and 25 hermit crabs last week so I'm waiting to see what happens.
On an interesting note, I could just be paranoid. I read that a cleanup crew should be replenished every three months. My crabs and snails could just be at the end of their life span, and the popping could very well be some sort of contraction (maybe something to do with temperature as it only happens right after my lights turn out for the night).

 

[RockingCricket]

Hmmmm....Well if it's any help I've noticed my cleanup crew dwindling too, but not nearly as dramatically as yours. I began my tank with a pitiful 12 hermits and 12 astrea snails and I'd say they have probably halved in 10 months.
Good luck with the new guys and thanks for the update *celebrate