Two Crab Deaths in Two Days?

[journey0820]

Hi there,
I found my spunky emerald crab dead yesterday and today found my mithrax crab dead also. Both were on their backs, both in different spots in the tank, but near to rock work.

I thought that I was mantis shrimp free but...could that be it? I only occasionally hear the "crack, crack" now and only at night. I've thought maybe it was a pistol shrimp but I've never laid eyes on whatever it is. Shoot, could be my hermits hitting the glass.

The other culprit might be my nitrate levels which have NEVER fallen below 20ppm though the tank has been running for about 3 months.

All of my other inverts, fish, and corals appear to be fine.

I can't do a thing about nitrates or a secret shrimp lair so I'm hoping ya'll have some other suspects...? Both crabs were original to the tank.

 

[Catpicklesdog]

Are you sure they're dead and it wasn't molts that you found?

 

[Reefscape]

If its a mantis, you will see damage on the crabs...Mithrax and Emerald are the same crab by the way, just different names...Your nitrates are nothing to be alarmed at, although they could be brought down some by larger water changes...

 

[journey0820]

Unfortunately, not molts. I pulled out the bodies. sad.

Are you sure they're dead and it wasn't molts that you found?

 

[journey0820]

Thanks...that is helpful. As it turns out then, I have 3 emerald/mithrax crabs...one has grown enormous...the other two just died. I'm wondering if there was inter-species war? Also, I was reading that their main food source is algae, which I have been eaten clean of (unless you count cyano which I don't think is really an algae anyway)...so they might have been out competed for limited food resources?

The red emerald/mithrax had a hole in the center of his abdomen which was eaten a bit...don't know if the damage was before or after death. Didn't notice or pay attention to the green one.

With the nitrates, big water changes only change them briefly and then the suckers climb back up. Never over 20...usually around 10. That's after adding cheato and xenia to the tank. Of course, it was previously stuck at 40 so I guess this is an improvement. I just worried I'd killed my crabs by prolonged nitrate poisoning!

If its a mantis, you will see damage on the crabs...Mithrax and Emerald are the same crab by the way, just different names...Your nitrates are nothing to be alarmed at, although they could be brought down some by larger water changes...

 

[tanker]

1) Crabs take months to starve, unless there is "0" (zero) food.
2) Emerald crabs do not "kill" each other.
3) Any other inverts in tank?? Crabs are very sensitive to water/chem change---Did you acclimate slowly??
4) Copper is a killer.

 

[journey0820]

I really appreciate all the ideas:

1. There hasn't been "visible" algae on the rocks...I don't know if he eats detritis, etc. I have green algae growth on the glass - like a film.
2. Dang.
3. Lots of inverts in the tank...hermits (way smaller), a cuke, snails...cuke has been nearly immobile for a month and small but no signs of the slimy death they go through. All other inverts seem okay. Porcelain crabs happy as can be. Corals seem good. I did a water change the day after their deaths...perhaps salinity was too high? It hovers around 1.24...wouldn't have been higher than 1.26.
4. Brand new tank, never used copper - no recent additions that might have carried copper in that I can think of.

Maybe I should get the last one out in case there is something that is going to kill him? I don't want to be a crab killer.

1) Crabs take months to starve, unless there is "0" (zero) food.
2) Emerald crabs do not "kill" each other.
3) Any other inverts in tank?? Crabs are very sensitive to water/chem change---Did you acclimate slowly??
4) Copper is a killer.

 

[tanker]

Salinety is fine. If other inverts are OK, I would leavae him in tank.

Also how did you acclimate?? Crabs, shrimps, need to be acclimated slowly (shrimps more then crabs).

 

[journey0820]

Salinety is fine. If other inverts are OK, I would leavae him in tank.

Also how did you acclimate?? Crabs, shrimps, need to be acclimated slowly (shrimps more then crabs).

Acclimation was about three months ago and was slow drip over the course of hours.

Strangely enough Myron, the mithrax I thought was dead IS ALIVE!! I saw him a minute ago...I don't know what to make of it. Either the second body was really a molt (but I would have sworn it was the REAL body...it had arms and everything) or I had a secret Mithrax crab in there I didn't notice and it was him, not Myron that died.

More confused than ever.

Feeling guilty last night, I took some algae from my fuge to see if the last big Mithrax would eat...he scarfed the whole thing down immediately!

 

[tanker]

LOL

Crab molts look just like the real crab, just no "crab" inside. If you acclimated 3 months ago---copper, poor acclimation, wrong salinety all goes out the window. I am glad it is still alive.