new creature in my tank (uninvited)

[Ryan Joel Smith]

So i went into my tv room last night and flicked the lights on (not tank lights) and noticed a quick movement on top of one of my rocks. What i believe was some sort of crab ran when there was any light at all in the tank so i could just barely see him in the crevas of a rock. I'm worried that this may be one of the crabs that are not good to be in a reef tank. Right now at blue world aquaria they have one of these crabs as a pet at the front desk and from what i remember it was a heavily amoured little critter that was white in color. What i saw in my tank didn't seem to be as bulky and had what i think was some black spotting........What do you think it could be and what kind of damage could it cause (worst case scenario). I really don't want to take my tank apart looking for him so i was thinking that if there were certain things a "bad" crab would do to my corals or fish i would monitor that and then take the appropriate action if he is in fact a threat to my reef....

[Marlin65]

Small glass or jar with some bait in it against a rock overnight.
Most crabs are bad. :twised: Better take it out if you can.

[Ryan Joel Smith]

what kind of bait would i put in that other fish won't go after? new to this whole "hunting of the crab" thing.

[Marlin65]

Small piece of shrimp or fish and put a rubber band tied to a small rock so it does not float away. Put it in at night when your fish are sleeping.

[lastlight]

Be prepared for frustration the likes of which you've never seen! I tried traps and one night got so fed up I sat there with a big knife in the water just above his rock for what must have been more than an hour. Left a piece of shrimp just under the knife. Stabbing a glass tank with a knife. SMART.

I'm sure my hand stunk more than the shrimp. I never caught the devil but I had a nice surprise one day when he just died on his own.

This is of little help to you but good luck!

[Ross]

Be prepared for frustration the likes of which you've never seen! I tried traps and one night got so fed up I sat there with a big knife in the water just above his rock for what must have been more than an hour. Left a piece of shrimp just under the knife. Stabbing a glass tank with a knife. SMART...

LOL thats too funny!:lol:

[Ryan Joel Smith]

Ok well i guess i should take my hand out of the tank now and put the knife away.....phew, my hand was getting pretty wrinkly. Are there any fish that hunt crabs that wonteat my corals?

[Marlin65]

Octopus but that will give you a whole other set of problems.
I have had good luck with the jar try that first or try to pull out the one rock he is hiding in.

[scub steve]

pull the rock he is in out of the tank and put it in sump

[Ryan Joel Smith]

Update*

So i went home yesterday to see that my timer on my lights was not working so the lights were off for a 24 hour period which nothing in my tank was too pleased with.

BUT i noticed the top fin on my large female clown was bitten off. as well my much smaller male clown had one of his fins nipped as well.......Thinking this seems to be more like the two fish fighting as they are new to eachother then the crab doing the damage. Any thoughts?

[RCFA]

When I first introduced my maroons, there was some fin nips for sure so this may be the case with yours, but I also had a gorilla crab. I noticed large sores on the sides of a couple of fish only to have the injured fish disappear the next night before I figured out what was going on. I did the whole trap thing, and it work surprisingly well. I put a shrimp tied to a piece of rubble in a plastic water bottle that had the end cut off and put it near the crab rock. Waited patiently with a red filtered flashlight and a net in the tank until about 12:30am and saw the crab venture out towards the bottle. I couldn't wait any longer so I shoved him the rest of the way into the bottle with the net. Gave him away to a mantis owner! :twised: