eletrocute a tank to kill a crab?

[salty joe]

A lot of crab restaurants electrocute crabs with regular old 110V. I am considering doing the same to my tank to lose a pest crab that will not enter any trap. I've only seen it twice. It looks like the shell is about 1 1/2 inches. I thought I could starve it out, I think it's still there. It's preventing me from stocking the tank.

Removing the rock is not a good option.

I acclimated a black molly to see if gets eaten, but the molly stays up by the overflow and keeps going over the overflow. I was hoping it would sleep in the rock...

It looks like I'm down to removing a couple pieces of rock and poisoning the tank or maybe try electrocution. I'm leaning towards electrocution so I don't have to deal with toxins possibly soaking into rock and sand.

I don't have coral or fish, just quite a variety of bugs and worms etc.

In terms of safety, I can do this without being dangerous using a momentary switch located away from the tank. I'd also use steel leads to keep copper out of the water.

One thing I'm not sure about is if the 15A breaker will trip right away with wires placed 5 or 6 feet apart in salt water. I could easily plug into a 20A circuit.

I'm not joking here, but there must be some good jokes here-I'm hoping for some good laughs and some serious input.

[reef thief]

Smoke it

[Joe0813]

I need to follow this one

[OrQidz]

Be safe, it sounds scary. I don't have any experience with purposely adding electricity to tanks, but just to throw this out there: Are you sure this crab will eat fish and be a problem? You said you have no coral or fish, I'm not sure if that's because the crab ate everything in the tank already. Crabs aren't great hitch hikers and are concerning for sure, but I'm not sure I'd mess with electrocuting a tank without being sure. Have you tried a small frag to see if it gets eaten?

[mattgumaer]

If you don't have anything in the tank yet, why not remove the rock? If you can put it in buckets with a little water in the bottom, chances are the crab will exit the rock for the water reasonably quickly. Seems much, much safer.

Matt

[salty joe]

Originally Posted by reef thief

Smoke it

Like, put it in a pipe and smoke it? Sounds like a mean way to euthanize a crab. But first I’d have to catch the dam thing.

Originally Posted by Joe0813

I need to follow this one

Glad you are here!

Originally Posted by OrQidz

Be safe, it sounds scary. I don't have any experience with purposely adding electricity to tanks, but just to throw this out there: Are you sure this crab will eat fish and be a problem? You said you have no coral or fish, I'm not sure if that's because the crab ate everything in the tank already. Crabs aren't great hitch hikers and are concerning for sure, but I'm not sure I'd mess with electrocuting a tank without being sure. Have you tried a small frag to see if it gets eaten?

I have not added coral or fish. One of the times I saw the crab; it was working on a snail. Cerith and other good snails are all gone except for little Collonista snails. I don’t want to add coral, wait out ich, only have that crab start picking off carefully QTd fish.

Originally Posted by mattgumaer

If you don't have anything in the tank yet, why not remove the rock? If you can put it in buckets with a little water in the bottom, chances are the crab will exit the rock for the water reasonably quickly. Seems much, much safer.

Matt

If only I could…It’s a big tank and before it had water in it, I built a fake boulder with dry rock and 3”, 2”, and 1” PVC bolt holes. There is no way that fake boulder is coming out in one piece. Plus, I secured my centerpiece old coral head to a sheet of PVC and siliconed it to the bottom. I wish I could take the rock out, but it’s just not a good option.
As far as safety, I‘d have a heavy duty momentary switch located away from the tank and I’d use heavy wire so the breaker would go way before the wire heated up to the point of failure. So no more chance of injury than turning on a light. I imagine it’d be a good idea to remove power heads and pH probe too.

Here's a pic of the kind of crab I have. This one is smaller than a dime, I found it on the underside of my algae filter a few months ago. I'm thinking he was running for his life.

[Apotack]

I would think you could find a simpler and safer way to remove the crab. If not please video and leave instructions for posting it here in your will.

[psidriven]

That actually looks like a porcelain crab, which is a filter feeder and pretty reef safe. Gorilla crabs and big sally light foots are the ones you need to watch out for.

[mgreenough]

I would drain the water from the tank and see if it comes out the rock looking for water. Safer than trying to electricute the tank.

[1jwampler]

How about buying a queen trigger from your LFS and sell it after it eats the crab?


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[TheFishGuy31]

Aside from leaving scorch marks on the glass of your aquarium (assuming the glass doesn't blow out) you'll be creating a dead short.

I'd recommend wearing sunglasses.


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[mgreenough]

How about something like this ;-)

https://youtu.be/wYZJEUXuEss

[Fiver]

Originally Posted by psidriven

That actually looks like a porcelain crab, which is a filter feeder and pretty reef safe. Gorilla crabs and big sally light foots are the ones you need to watch out for.

That does look like a porcelain crab. They have six legs in addition to their claws. The undesirable crabs have eight legs in addition to their claws.

I have a few dozen porcelain crabs, and they are completely harmless. I love mine.

[johnike]

Originally Posted by Joe0813

I need to follow this one

Hiya stranger!

[Silly clownfish]

What about putting in every heater you can get your hands on and crank the tempurature up to something ridiculous for about a week? I like the draining the tank idea too, probably better.

With any method, how will you be able to verify it is dead? If you electrocute it, it could just stay dead in the rock. You won't know that it is actually dead. That's what I like about the draining the tank idea, you have the best chance of seeing it.

[Mrs. Music]

Draining the tank and flush a peroxide wash over the rocks you think he is in with a turkey baster would work well.

[salty joe]

Thanks for pointing out it looks like a porcelain crab. I mistakenly thought porcelain crabs had sieves instead of claws, not as well as claws...I can't be sure if the one I'm after is a porcelain too. Would a porcelain crab eat a snail? Are they nocturnal?

Originally Posted by Silly clownfish

With any method, how will you be able to verify it is dead? .

Yeah, that's a problem. Even if I drained the tank, I think the crab would stay in the fake boulder even with peroxide. There are just soo many nooks and crannies-it's good sized.

I did consider an undulated trigger, but the crab stays tucked in the rock. I also thought maybe an octopus. I've never seen one in a store though.

Or maybe toss an M80 in and hope it goes viral on youtube. Ha, that was a good one!

Raising the temp is a good idea, thanks. Just shutting down the cooling system would do it. Much better than electrocution. Knowing the crab I'm after might also be a porcelain crab, makes me cool my jets a little.

Thanks for the good ideas and input.

If I could get a do over, I'd put the live rock in its own tank for a couple months to see what's on it.

[Fiver]

Originally Posted by salty joe

Thanks for pointing out it looks like a porcelain crab. I mistakenly thought porcelain crabs had sieves instead of claws, not as well as claws...I can't be sure if the one I'm after is a porcelain too. Would a porcelain crab eat a snail? Are they nocturnal?



Yeah, that's a problem. Even if I drained the tank, I think the crab would stay in the fake boulder even with peroxide. There are just soo many nooks and crannies-it's good sized.

I did consider an undulated trigger, but the crab stays tucked in the rock. I also thought maybe an octopus. I've never seen one in a store though.

Or maybe toss an M80 in and hope it goes viral on youtube. Ha, that was a good one!

Raising the temp is a good idea, thanks. Just shutting down the cooling system would do it. Much better than electrocution. Knowing the crab I'm after might also be a porcelain crab, makes me cool my jets a little.

Thanks for the good ideas and input.

If I could get a do over, I'd put the live rock in its own tank for a couple months to see what's on it.

Porcelain crabs have regular crab claws, but then they have two small arms/appendages near the mouth/in between the claws that have large fans on either end. They use these arm fans to reach out and grab/filter food from the water column. Mine also pick at the gravel. They won't go after snails, shrimp, corals, fish, etc.

They are most active at night, but mine come out at all hours.

Here's one of mine:

[mgreenough]

Best method then to live catch is the baited jam jar. Place a tall jar next to the rock where the crab is at an angle and place food inside. The crab should get stuck in the jar if it gets inside. I could not do that in my tank as the shrimp/nass snails used to pinch the food before any crab could get a look in. Since your tank is empty it may work.

[salty joe]

I tried the tall jar against the rock, the trap with little acrylic fingers that make a one way trap door, guillotine trap door and inverted funnel, all for at least a week at a time. The only time I got even close was the guillotine trap door had the bait taken after thee or four nights. I put a red light over the tank to see the guillotine trap and the crab would not take the bait. The night I turned the light off, the bait was taken sometime between 3 and 6 AM.

[saf1]

Electricity seems a bit overkill. I would continue to try the traps and use a piece of shrimp or prawn. Also mash up a bit of the food to get the smell going.

Honestly, and not to make light of it, just make a game out of it. Use a Tupperware container, slot the top, toss in the shrimp and mush, put some sand / substrate over the top, see what happens. I had to catch a Gorilla crab once and this is what I ended up doing although I actually put a fishing swivel through the lid and base, some line, and added a rock inside to weigh it down. Then I picked a weekend, loaded it up, and waited for it to get there and snack. Then pulled it. It couldn't get out

Anyway - bummer for you and sorry to hear about the frustration. Hang in there. You will win in the end.

[Joe0813]

Originally Posted by johnike

Hiya stranger!

Hey John how are you ?

[Joe0813]

If you do go the electric chair method please video it... I want to see how it goes

[ReefCowboy]

This is funny...made me laugh when i read it

[Darryl Hey]

yeah video this insanity
I could use a good laugh