Help - Emerald Crab Genocide

[OmegaOmega]

I did a 20% water change yesterday morning but today realized that all my emeralds weren't out in front crawling around. I looked in the back and they were all dead, together.

I had four emerald crabs - two had just molted a week ago - all seemed active and healthy but I'm confused what would have caused their deaths? The sally light foot is still alive and doing fine (even feeding off the dead ones) and the corals and fish appear to be fine to including the featherduster. I've tested and everything came back good as well - my salinity was slightly lower than from before I did the water change, but I think that's just because of evaporation from beforehand since I did not top off.

I would think that the reason they're all bunched together is because that may be a possible dead spot of water movement in the tank, but has anyone seen this before? Is there a disease just crabs can get - if so; why wasn't the sally light foot impacted? Are crabs more sensitive then fish? Are there any dosing items that can kill them? (Magnesium, calcium, etc?)

 

[PufferGuy]

I have 2 emeralds in my 40gal and when they happen to be in the same area they sometimes go at it untill one of them runs away. I think 4 emeralds in a 29gal is a bit too much so they might have met in an area and then killed eachother.

Also, copper can kill inverts pretty quickly depending on the level of copper in the water, so that would be anothe thing to check for.

 

[OmegaOmega]

The emeralds have never fought before - space doesn't seem to be an issue, and I could definitely see a couple fighting if it were, but all four?

I thought copper could be an issue, but like I said - everything else is fine including the one sally light foot crab and tests came back negative unless it's not sensitive enough to pick up trace copper; which I'd assume wouldn't be an issue. I use RO water.

Just seems odd - four crabs, one location, all dead over night.

 

[dcantucson]

:shock: Maybe they took a suicide pact? :shock:

In a 29 gallon unless you had a lot of green for them to eat they could starve! Were you feeding them?

 

[AdeptMrSniffles]

I guess I'll be the one to say it.

Sounds like they drank the cool aid.

I haven't bought an emerald crab in 6 months. They always seem to die on me in a week or so.

 

[yote]

Thats one that may never be answered.:dunno:

 

[Rcpilot]

They fight and kill each other. I never could keep more than 1 in the same tank. Even when my 10g frag tank was almost completely overgrown with algae, the big one killed 2 smaller ones in less than a week. Didn't matter that there was more than enough food for them to last months and months.

I don't know who in the heck ever came up with the idea these emerald crabs were peaceful herbivores........ in my experience they are just like any other crab. Opportunistic killers that will eliminate the competition and attack anything they can catch.

 

[dcantucson]

Hey watch the crabby talk! :lol:
If that is true which crab killed the last crab? Well, maybe he killed himself from over eating! :lol: :mrgreen:

 

[Rcpilot]

The last crab (biggest one) finally just up and died. Don't know what got him.... :dunno:

I'm done with crabs. But we won't go there today. :mrgreen:

 

[OmegaOmega]

:shock: Maybe they took a suicide pact? :shock:

In a 29 gallon unless you had a lot of green for them to eat they could starve! Were you feeding them?

There's some green and plenty of brown algae - plus I will hand feed them some sinking granules each morning; so I'm under the impression they get a decent amount to eat.

Thats one that may never be answered.:dunno:

One or two I'd understand - but all four dead at the same time while the sally light foot and hermits, fish, etc are perfectly fine? Suspect.

Are crabs sensitive to salinity?

 

[Rcpilot]

Are crabs sensitive to salinity?

YES

Inverts are ESPECIALLY sensitive to salinity. Snails, crabs, worms etc are all very sensitive to changes in salinity. It's their kidneys and other internal organs. They are like 98% water. Rapid changes in salinity cause organ failure. Mostly kidney failure. After that, it's just a matter of time before they die from it. Could be a couple days, could be a few weeks.

Bringing them home from the LFS and just plunking them in the tank after a quick 20 minute acclimation or even NO acclimation is a death sentence to them.

Thats why I acclimate for at least 3 or 4 hrs. 6-8hrs would be better.