Why do my shrimp die when they molt?

[redfishsc]

Twice I have had shrimp die during or just after a molt.

First it was the one peppermint shrimp I had. I noticed he was having some difficulty in the molt, he spent the better part of the day with his shell partly intact and him acting as if he were in a panic. He was the only shrimp in there.

Later I put in a CB shrimp, and all was well until he molted 3 weeks later. I found his shell, empty, but he never surfaced. He has been missing for 2 weeks now. Note that this is a small tank, so he's not "lost in the rocks" (see tank description below)

None of my fish are big enough to even think of eating a molted CB shrimp. The only predators I would suspect tackling a soft shrimp would be the small handful of blue hermits or one of my two emerald crabs.

Everything else in the tank is in fantastic shape and growing well.

Some have suggested iodine/iodide, but I know also that Randy does not think it is necessary (of the group, I trust Randy by FAR).

Parameters
Water changed 10% weekly
Salinity 35ppt (IO)
nitrite, ammonia --0
nitrate, 0-2ppm
calcium, 420ppm
kalk 8dKH
pH--- 8.2

[schristi69]

Last I read shrimp need Iodine to help in the molting process. Mine never had any problems and I dosed Iodine about every 2 weeks.

[woodiecrafts]

I would almost bet the emerald crabs are enjoying the snack of the soft shrimp once his shell comes off. I myself don't think that Iodine would be an issue unless you haven't done any water changes in months, and I rather doubt that as well.

[TheH]

I agree with woodiecrafts, if your shrimp are dying during molts there may be something eating them. Perhaps a mantis or something you may have added to the tank yourself.

[IFbettas]

The emerald crabs sound suspicious. Sometimes they are peaceful, but there are always those rogues that are really aggressive.

[divewsharks]

the CBS is also a definite candidate, mine is large, and has taken two smaller shrimp during molts.

EDIT:: sorry misread the post. CBS is the victim..

[Billionzz]

Sometimes stress will cause them to molt.

Are you sure it's not something that going on with your water?

[redfishsc]

Billionzz, not so far as I can tell. I keep my SG 35-36ppt (refractometer) and I have no nitrates (2ppm or less, way below the 5ppm that the API can detect). That, and I have nearly no nuisance algae which tells me that the nitrates are extremely low.


Temp stays constant 78-79 (the heater and the cooling fans duke it out and keep surprisingly constant).


I was careful to acclimate both shrimp (which were never in the tank together) with a drip.

I dunno, beats me.

[Madfronter]

I would say the CBS is most likely the culprit. I would assume the CBS doesn't having molting issues? Though the addition of iodine couldn't hurt.

[woodiecrafts]

Redfish, is there anyway you could isolate the Emerald crab for a few weeks and try another shrimp. If the same thing happened, you would at least know it is not the crab. Just a thought, might not be practicle, but would remove one possibility.

[surge19us]

You say you don't suspect the fish. What fish do you have? Just read your sig line. You have all that coral and fish in a 10g? Seems like a lot. The damsel is suspect. More likely the shrimp is more susceptible to some tank parameter, from overcrowding, after molting.

[tigereye37]

Do you dose Iodide by any chance? THat can cause a pre-mature molt and can be toxic in high quantities.....

[asonitez]

According to his sig... i'd say the bullshark.

[redfishsc]

Originally posted by Madfronter
I would say the CBS is most likely the culprit. I would assume the CBS doesn't having molting issues? Though the addition of iodine couldn't hurt.

The CBS was never in the tank at the same time as the peppermint (I didn't clarify that) and both the peppermint and CBS died similar deaths.

[redfishsc]

Originally posted by woodiecrafts
Redfish, is there anyway you could isolate the Emerald crab for a few weeks and try another shrimp. If the same thing happened, you would at least know it is not the crab. Just a thought, might not be practicle, but would remove one possibility.

Good idea. I do have a 4-gallon sump on this tank I can use as a solitary.

Originally posted by surge19us
You say you don't suspect the fish. What fish do you have? Just read your sig line. You have all that coral and fish in a 10g? Seems like a lot. The damsel is suspect. More likely the shrimp is more susceptible to some tank parameter, from overcrowding, after molting.

All of the fish are quite small, none of them are bigger than 2" long. I suppose they could have harrassed the shrimp and nipped it to death.

As for the corals, they are all small frags. The tank's not even close to "overcrowded" although I do admit it looks like a LOT for a 10g by the way my sig reads.

Originally posted by tigereye37
Do you dose Iodide by any chance? THat can cause a pre-mature molt and can be toxic in high quantities.....

I don't dose iodide, for the reason that you mention. I know too much is a LOT more dangerous than supposedly too little.

Originally posted by asonitez
According to his sig... i'd say the bullshark.

Emphasis on the bull

[Electrobes]

What are your regularly feeding habits? Maybe the crabs are suspicious because they are hard press for food? Total shot in the dark... but looking at your tests everything should be hunky-dory.

Only other thing I can think off are unseen metals maybe or something that you haven't tested for. I find this to be of little possibility only because if this were true.. your other janitors would be having problems too.

[justinl]

ever had any exposure to copper?

[mrpenguin]

Dont they give off some sort of hormone or something when they molt ? I seen my moray eel attack and eat my shrimp right after he molted even though they were living peacefully for months together.

I was told lots of fish, crabs and eels would go after a shrimp right after it molted.

[tkeracer619]

Originally posted by redfishsc


Emphasis on the bull

too funny

I would have iodine tested but other then that no real idea other then the shrimp not having an adequate hiding spot during the molt and some critter enjoying shrimp dinner. If you do water changes, chances are iodine levels are fine.

[redfishsc]

Originally posted by Electrobes
What are your regularly feeding habits? Maybe the crabs are suspicious because they are hard press for food? Total shot in the dark... but looking at your tests everything should be hunky-dory.

Only other thing I can think off are unseen metals maybe or something that you haven't tested for. I find this to be of little possibility only because if this were true.. your other janitors would be having problems too.

Flake food daily, mysis and cyclop-eeze every other day. I used to feed fairly heavily and had some small hair algae outbreaks, so I started rinsing the mysis before using them and cut the cyclop-eeze to half, and the hair algae went away.

I may be feeding a bit lighter than my crabs would prefer. I may still put one of them in the fuge where there's tons of goodies to eat on, the tank itself has been cleaned pretty bare.

Originally posted by justinl
ever had any exposure to copper?

Not that I am aware of. There are no copper components in the tank and I use RO/DI or distilled water for mix and topoff.

Originally posted by mrpenguin
Dont they give off some sort of hormone or something when they molt ? I seen my moray eel attack and eat my shrimp right after he molted even though they were living peacefully for months together.

I was told lots of fish, crabs and eels would go after a shrimp right after it molted.

I dunno about hormones, but I am sure they do put off something fish and other preds can smell.

FWIW I'd never put a small crustacean in with a moray.

Originally posted by tkeracer619
too funny

I would have iodine tested but other then that no real idea other then the shrimp not having an adequate hiding spot during the molt and some critter enjoying shrimp dinner. If you do water changes, chances are iodine levels are fine.

Yep, that's what I suspected about iodine and water changes. Randy Holmes-Farley has said, I believe, that there isn't a reliable way to test for iodine (regardless of what kit mfr's say).