The Freaks come out at night. Crabs, Crabs, and more Crabs.

[EL Diablo]

Hey all,

I am just about ready to add my first fish.
I was leaning toward community fish but now I am not so sure
I am thinking aggressive now.

Last night with all the lights out I searched my tank with a flashlight.
Man do the freaks come out at night.

I found at least a dozen crabs hidding in all the nookes and cranies in the LR. most were small but at least one was a little bigger than most.

I even found one munching on a snail. When I shined the light on him he just looked up and then continued on munching.

I also have a few clickers in the tank, A Mantis or a Pistol. not sure and I cant find him.

I dont want to tear the tank apart looking for hitchers.

Anyway I think it would be close to impossible to catch all the crabs.
I am thinking a few aggressive fish will eat them up for a snack.

I am worried that community fish will get killed by the crabs sooner or later.

What do you guys think? would community fish thrive in this Crab enviornment or just end up as crab food.

Would aggressive fish be better to keep and eventually eat the crabs?

I would like to try coral next year when my tank is more established but not with the crabs in there. if I can have a good variety of aggressive live stock I would go that route, I just dont like to have large fish in a smallish tank. Would they do ok in just a 72 gallon tank?

Any suggestions?

Thanks

[ClamKnuckle]

I suggest trying to catch the crabs rather then getting a fish that later down the road you don't want

If you know where they live (what rock) you can set a trap by placing a a hunk of shrimp or other fresh seafood in a jar near the rock...the crab will go in to get it but can't get out

another method is to do a dip on the LR if you know a crab is living in it...i've read a lot of different ways to do this, wether it be with fresh water, high salinity or with carbonated water (i would ask or do a search before dipping anything because you can hurt the stuff you want in the tank)

I've gotten lucky and have had my crabs out when the lights are on and have been able to pull out the rock they were on and just grab them off

HTH

[EL Diablo]

I think I may try the jar and shrimp method.
I really dont want to start pulling out the rock and dipping.

What kind of shrimp do I get?

I guess I can set up the trap at night and remove it in the morning.
I saw athread with a wine glass and it seemed to do the trick.

Will leaving the shrimp over night affect my water levels?

Thanks

[ClamKnuckle]

when i did it and just left it in over night i did not see any change in my levels at all...not too much time for it to start breaking down really

I know other people have done this method as well and its been successful for them

don't be discouraged if you don't get something on the first try though

i would just get some thing that is fresh and wasn't frozen so you know you don't have any sort of preservative or anything in there

[Atari]

Yes it's very important to use fresh seafood (and replace it daily if not successful). Otherwise you'll just be feeding the algae.

[Foible]

I used the soda bottle trap method. Take a soda bottle (2 liter) and cut off the funnel-like end and maybe cut the pouring spout off if you think your crabs won't fit into it. Stick the top of the bottle facing into the bottle and punch holes in both pieces so tyou can tie it in. Some people just tape or staple it. Then stick any fresh or frozen type seafood into the bottle and change it daily. I got some the very first night.

[EL Diablo]

My first attempt last night resulted with Zero crabs.
I noticed my hitchhiking Goby hanging out by the trap for a quick meal.

The crabs will be had!
Tonight we try again.

[lando]

If you plan to start a reef down the road, you might want to consider getting fish that are reef safe from the start. It can be a real pain to catch fish with all the LR in your tank when you decide it is time for them to go. Just a thought.

[EL Diablo]

Originally Posted by lando

If you plan to start a reef down the road, you might want to consider getting fish that are reef safe from the start. It can be a real pain to catch fish with all the LR in your tank when you decide it is time for them to go. Just a thought.

I agree. I dont want the crabs to dicate what fish I get.
Altough the idea of the crabs becoming a snack for a trigger does sound appealing.

I can see it's going to be difficult to get them all out. Just need to be patient.

[quarryshark]

Depending on the type of crab, thay may not be all bad. Have you IDed them? Some are algea eaters. Where did you rock come from?
I have 2 Emerald Crabs, one of them is very big and has never bothered anyone.
I recieved 8-10 crabs on my LR, got them along with a few pistol shrimp in a cabonated water dip looking for mantis . A couple were decorator crabs and some I didn't know. I added them to the system, IMO it adds to the diversity to my tank, after all I want a mini ocean. If anyone gets too big or starts causing trouble, I will get him out.
Just another opinion.

[EL Diablo]

Originally Posted by quarryshark

Depending on the type of crab, thay may not be all bad. Have you IDed them? Some are algea eaters. Where did you rock come from?
I have 2 Emerald Crabs, one of them is very big and has never bothered anyone.
I recieved 8-10 crabs on my LR, got them along with a few pistol shrimp in a cabonated water dip looking for mantis . A couple were decorator crabs and some I didn't know. I added them to the system, IMO it adds to the diversity to my tank, after all I want a mini ocean. If anyone gets too big or starts causing trouble, I will get him out.
Just another opinion.

Thanks for the Advice. Kinda what I wanted to hear

I have 80# of keys rock from LR.com

I am going to try and get pics and detailed descriptions
of all the crabs. I've spotted at least 6 and I have clicking
from the tank from at least 2 different spots. Mantis or Pistol?
He never comes out. I've searched the tank at night with a
flash light but can’t find them.

I do know I have one that has fans as arms and waves them like he's
catching something. He is very small and cool looking. I
think it's a porcelain crab. I hope the other crabs don’t kill him.

I also don’t want to disrupt the live rock. It's doing great
and I notice new things on it daily. I just discovered some
big worm poking his head out of a hole.

I would love to keep all the crabs if I knew they were relatively
safe. I just discovered a few bubble algae balls and an Emerald
would come in handy. I am just worried they will mess with the fish.
I caught 2 munching on a snail. I am still not sure what
fish I am going to get either.

Is it possible for the crabs and fish to co-exist?
or do I need to go with certain fish?

I don’t want to do a dip. I tried a trap last night and
got nothing. Catching all these critters would be a pain
in the rear. Plus I am ready for my first fish and don’t
want to wait a few weeks while I hunt down all the crabs.

If I saw 6 of them I am thinking there is at least double
that in the tank that I didn’t see.

trying to figure it all out

Thanks for all the advice.

[quarryshark]

The clicking, is it rapid or random, single clicks? If its random single, then its most likely a pistol shrimp. If its rapid fire, then it may be a Mantis.
As for the crabs, its your call. Some hate crabs and some (myself included) think they are cool and add to the tank.
Lot of gray areas in this hobby, maybe some others will chime in and you will have enough info to make a decision. I know its tough sometimes.
Most of all enjoy!!

[EL Diablo]

sometimes the clicking is a few in a row and sometimes its just one.
I got rid of one Mantis when the LR was delievered. got lucky and found him swiming in the plastic bag the LR came in.

Love to see who is the culprit!

[mle421]

i know this is a really really really old post, but im curious about what happened? i have the same problem, and i read elsewhere on this forum that the clicking could be these crabs! so im anxious to know if your crabs were good or bad, and if you got fish with them and how they worked with the crabs!

[Jonathan G.]

Yea i didnt know crabs hurt the fish for live rock... i havent set up my tank yet but i was gonna definitly add a couple emerald crabs and some red and blue legged hermits. I thought that the live rock and tank would benefit from these crabs, dont they help with detrius or whatever that word is?

[mle421]

emerald and hermit crabs do but not all crabs, some kill snails and other inverts, i'm hoping i don't have the bad kind

[tmcpeek]

I just caught all my crabs excpet for a sally lightfoot with the 2 liter bottle method. I used a frozen cube of brine shrimp whole in the package and poked holes in the foil with a needle. I caught a arrow and 2 emeralds the first night. I was unlucky with my crabs. I watched the arrow snag a blood shrimp within 15 minutes of introducing the shrimp. My emeralds were eating snails and hermits (never touched the bubble algae) so I decided to get them out.

Good luck.

[mle421]

hmmm good to know. they don't harm fish do they? i just brought home two little percula's and i doubt the crabs could even catch them but i'd rather be sure they'll be alright

[EL Diablo]

ok here is a looooooooong Update 5 months later

I upgraded my lights soon after I set my tank up and started adding corals. Now I really wanted to get the crabs out.

I tried to catch the crabs with the titled glass and shrimp method.
night after night nothing

I gave up for a few weeks

Then I borrowed a fish trap from my LFS that had a drop door triggered when you released a fishing line. I had to sit and wait forever and a crab never went in.
My fish did.

I gave up again.

All the while I continued to hear clicking from the tank. never seeing what caused it.

I started adding more and more Corals and worried about something munching on them. So I finally came across a trap called the Xterminator.

The first night I placed the Trap I caught a Big Hairy Crab. Turned out to be
a Rock Crab, Not Reef Safe. The next night the same exact thing. A smaller guy.

I brought the crabs to my LFS where the owners son happily fed them to his huge Peacock Mantis.

I placed the trap a few more nights but came up empty handed.
over the next few weeks I found a few crabs dead and a few crab claws in the sand.

So I got tired off setting the trap every night. My six line wrasse actually ended
up in it one time. I didnt see any crabs and none of my corals were touched.

Finally 4 months after hearing the clicking I saw him. He saw me too.
A Peacock Mantis Shrimp. he was about an inch or less.

I was like "Oh Cool" and "Oh #$%@ " at the same time 8O

and thats where we are today. I havent seen any crabs in a long time. I am sure if I look I might find one hanging somewhere.
As for the Mantis, I havent seen him since but hear him everyday. his popping is as loud as a finger snap. Sometime he clicks just once and sometimes he clicks a few in a row.

Everyweek end I plan to catch him. just havent set the trap. Actually I plan to set the trap where I think he hangs this week-end. Right now he appears too tiny to get a fish. I still have a few of my hermits but I am sure he hunts them down and will get all of them eventually.

The owner son of the LFS wants the Mantis. I told him I'll trade him for a Ricorda shroom.

I'll let you guys know how it goes and when I get my Ricorda

[mle421]

thanks for the update! ive seen a few hairy crabs but they're pretty small, i'll look into that trap!