Fiddler Crab Question

[biocalluna]

Hi!

I have a 20 gallon tank with 9 male fiddler crabs living in it (there were 10
but one of them passed earlier this week :[ )

The tank is divided up into thirds - the two outer thirds have sand, the middle third has brackish water and a filter. It's covered with a screen and has a heat lamp. I've had these guys for almost two months - originally they were in isolation tanks for my animal behavior lab (they weren't harmed or treated poorly during the experiment - it was purely observational) and I introduced them to the 20 gallon tank all at once.

Some of the larger ones seem to be fighting for space in the water and I think poor, tiny Arnold got caught between some of the big guys while they were fighting because he's now missing his large claw!

I know it will grow back on the opposite side during his next molt - would it be best to try and isolate him until he molts and grows his large claw back?

I moved him onto the sand and he got comfy in one of the water dishes I have set up there so he's out of the way of the big crabs for now but I'm worried because I think that's how the tenth crab (he was tiny, too) died and he doesn't have a big claw for defense anymore

Thank you!

 

[biocalluna]

He hung out in his own space awhile then went back into the rest of the water and seemed fine but this morning I got up and found that he'd died and was missing another leg.

Either the big crabs are being jerks or he was losing limbs from stress but this post is irrelevant now
Sorry Arnold.

 

[Tbox]

RIP Arnold.

A fiddler crab setup sounds like a fun project.
So, as long as a female fiddler isn't in the tank with the remaining 9 males, aggressive behavior will be just moderate? ^^except for poor Arnold^^

The males look like gladiators designed to do one thing, fight. Do they require territories?

 

[biocalluna]

Yeah I'm down to 7 crabs now one died earlier this week (he looked like he got caught up in a fight between bigger crabs) and then Arnold passed, and another one died later this morning, I think from stress. He was blowing bubbles and hanging out in a water dish with Arnold and wasn't doing great but he wasn't injured. They can die from frustration so that may have been a problem.

I cleaned the tank today and got them some fresh water. Since there are only 7 on a 20 gallon tank they seem to have calmed down considerably. Asimoff is a jerk sometimes and Francis likes to instigate. Cecil is always rude.

They are very territorial and had plenty of space to begin with but perhaps they felt they needed more. I'll post a picture of my set up! They're fun to watch.

They have plenty of hidey holes (some sand castle things and a couple of rocks that passed the vinegar test). I keep their food in separate water dishes so their water doesn't get cloudy.

If you look close you'll see 6 in the water (one hiding behind the ramp and one on the filter) and the 7th is in the water dish with the food. There's another ramp but some shells fell off so I've removed that until the tank glue is dry.

 

[Toad]

I've never see a fiddler set up like that before, I've always seen ones with more water and small beach areas/out of water spaces.

Sent from my SM-G930T using Aquarium Advice mobile app

 

[biocalluna]

I have 7 male fiddler crabs and they're territorial animals so I set them up with plenty of space. I have the water and sand divided with plexiglass because I have a pulled muscle in my back (fun fun) and I can't really clean a bunch of heavy wet sand - it just makes cleaning the tank easier.

They aren't fighting over space in the water or on the beach spaces so it seems to be working out fine

 

[ArcudiElizabeth]

Is it okay if I steal this layout idea in the future? Also what did you use to secure the rocks on the plexi?

Yeah I'm down to 7 crabs now one died earlier this week (he looked like he got caught up in a fight between bigger crabs) and then Arnold passed, and another one died later this morning, I think from stress. He was blowing bubbles and hanging out in a water dish with Arnold and wasn't doing great but he wasn't injured. They can die from frustration so that may have been a problem.

I cleaned the tank today and got them some fresh water. Since there are only 7 on a 20 gallon tank they seem to have calmed down considerably. Asimoff is a jerk sometimes and Francis likes to instigate. Cecil is always rude.

They are very territorial and had plenty of space to begin with but perhaps they felt they needed more. I'll post a picture of my set up! They're fun to watch.

They have plenty of hidey holes (some sand castle things and a couple of rocks that passed the vinegar test). I keep their food in separate water dishes so their water doesn't get cloudy.

If you look close you'll see 6 in the water (one hiding behind the ramp and one on the filter) and the 7th is in the water dish with the food. There's another ramp but some shells fell off so I've removed that until the tank glue is dry.

 

[biocalluna]

Yeah, go for it. I used aquarium epoxy to attach the plexi glass dividers to the tank, and the shells to the plexi glass ramps. It worked well for the dividers but it took a while because it needs 24-48 hours to dry and it needed to dry before I could check for leaks.

It didn't hold as well on the shells for the ramp but I think that's because shells are calcium carbonate and not plexiglass

All my poor crabs are gone now. They didn't much like being moved from iso tanks to a shared tank. Good luck with yours

 

[ArcudiElizabeth]

Yeah, go for it. I used aquarium epoxy to attach the plexi glass dividers to the tank, and the shells to the plexi glass ramps. It worked well for the dividers but it took a while because it needs 24-48 hours to dry and it needed to dry before I could check for leaks.

It didn't hold as well on the shells for the ramp but I think that's because shells are calcium carbonate and not plexiglass

All my poor crabs are gone now. They didn't much like being moved from iso tanks to a shared tank. Good luck with yours

I only have 1 crab and he's very happy but it's just for the future maybe. But thank you! I'm sorry for the loss of your crabs

 

[idol1]

It looked like the sand was dry?

The fiddlers need the wet sand.

That's where they will build their borrows.

If it was my build. I would not seal the bottom portion of the plexi.

I would of made it so the sand could absorb the water from the bottom by seepage.

They need the wet sand. Fiddlers don't like spending time underwater.

 

[Tbox]

Good points idol. They're basically land crabs that sieve through wet sand for food paticulates. I've never kept them, just experience catching other similar crab species in and around the Pacific. A rocky shoreline(under the rocks) will be covered with: Yellow shore crabs, hairy shore crab, green shore crab,
mud-flat crab, and Oregon shore crab
(Hemigrapsus oregonensis)

Even a species like dungeness, a fully submerged species, will live for 24hrs on ice. They still have their lungs from long ago. Keep them cool, calm and chilled/out of the sun and they're good until water boiling time in the evening; )

It looked like the sand was dry?

The fiddlers need the wet sand.

That's where they will build their borrows.

If it was my build. I would not seal the bottom portion of the plexi.

I would of made it so the sand could absorb the water from the bottom by seepage.

They need the wet sand. Fiddlers don't like spending time underwater.