Blue Knuckle Hermit Crab

[Ndryden]

Hello, i’ve now gone through 4 Blue Knuckle Hermit Crabs. All 4 have died the same way but I can’t figure out why. They are in a Fluval 13.5 gallon tank with two clown fish. All of the parameters seem perfect and they eat the first day. About 2-3 days in they start to fall apart (Like literally all of their limbs falling off) and eventually crawl out of their shell and die. I haven’t been able to find anything on this, any help would be greatly appreciated. Copper, Iron, Nitrate and Nitrite, and Chlorine are all zero. Salinity is 1.024, 76 degrees F, Ph is somewhere around 7.8. I thought this may be molting at first but their shell is empty and they will sit there dead for days with no movement.

 

[ISpeakForTheSeas]

Hello, i’ve now gone through 4 Blue Knuckle Hermit Crabs. All 4 have died the same way but I can’t figure out why. They are in a Fluval 13.5 gallon tank with two clown fish. All of the parameters seem perfect and they eat the first day. About 2-3 days in they start to fall apart (Like literally all of their limbs falling off) and eventually crawl out of their shell and die. I haven’t been able to find anything on this, any help would be greatly appreciated. Copper, Iron, Nitrate and Nitrite, and Chlorine are all zero. Salinity is 1.024, 76 degrees F, Ph is somewhere around 7.8. I thought this may be molting at first but their shell is empty and they will sit there dead for days with no movement.

Welcome to Reef2Reef and sorry for your trouble!


A few questions to kick troubleshooting things off here:

- Have you seen the limbs falling off, or do you just see them with the limbs one moment then missing them the next?

- Is it possible you could have something attacking/eating them in the tank?

- Is there any chance your tank has some harmful contaminants in it? (Think like cleaning chemicals, toxins, exposed metal/rust, etc.)

- Have you tried cutting open any of the dead hermits to check for meat inside? (That would tell you for sure if they are molts or not.)

- Do the hermits have other, larger shells they can change into when they molt?

- What parameters are you testing, and what specific results are you getting for each? (As a note, Nitrites aren't harmful in saltwater, so most people don't bother testing for them; Nitrate being 0 is actually a bit odd and could probably stand to be raised a bit.)

- What water are you using? (Tap, RODI, sea water, LFS water, etc.?)

 

[Ndryden]

Welcome to Reef2Reef and sorry for your trouble!


A few questions to kick troubleshooting things off here:

- Have you seen the limbs falling off, or do you just see them with the limbs one moment then missing them the next?

- Is it possible you could have something attacking/eating them in the tank?

- Is there any chance your tank has some harmful contaminants in it? (Think like cleaning chemicals, toxins, exposed metal/rust, etc.)

- Have you tried cutting open any of the dead hermits to check for meat inside? (That would tell you for sure if they are molts or not.)

- Do the hermits have other, larger shells they can change into when they molt?

- What parameters are you testing, and what specific results are you getting for each? (As a note, Nitrites aren't harmful in saltwater, so most people don't bother testing for them; Nitrate being 0 is actually a bit odd and could probably stand to be raised a bit.)

- What water are you using? (Tap, RODI, sea water, LFS water, etc.?)

I don’t personally see the limbs fall off, when i come home from work there is usually just some libs sitting next to them, as far as attacking them the only other thing i have in the tank is two small clown fish and they seem to curiously swim near the hermits but i’ve never seen them attack. No harmful chemicals, i would assume that would effect the clowns too. I could try cutting open the hermit that is in the tank now, yes there are larger shells, one of them swapped to a smaller shell the first day. I’m using tap water that i have filtered with a reverse osmosis system, as for testing i just use some test strips, here is what the crabs always do after a couple of days

 

[Ndryden]

Welcome to Reef2Reef and sorry for your trouble!


A few questions to kick troubleshooting things off here:

- Have you seen the limbs falling off, or do you just see them with the limbs one moment then missing them the next?

- Is it possible you could have something attacking/eating them in the tank?

- Is there any chance your tank has some harmful contaminants in it? (Think like cleaning chemicals, toxins, exposed metal/rust, etc.)

- Have you tried cutting open any of the dead hermits to check for meat inside? (That would tell you for sure if they are molts or not.)

- Do the hermits have other, larger shells they can change into when they molt?

- What parameters are you testing, and what specific results are you getting for each? (As a note, Nitrites aren't harmful in saltwater, so most people don't bother testing for them; Nitrate being 0 is actually a bit odd and could probably stand to be raised a bit.)

- What water are you using? (Tap, RODI, sea water, LFS water, etc.?)

Here is a photo of the test

 

[ISpeakForTheSeas]

I don’t personally see the limbs fall off, when i come home from work there is usually just some libs sitting next to them, as far as attacking them the only other thing i have in the tank is two small clown fish and they seem to curiously swim near the hermits but i’ve never seen them attack.

It's unlikely, but I'd say to set a camera to record the tank while you're not in the room and see if one of the clowns is going after the crab while you're not there.

No harmful chemicals, i would assume that would effect the clowns too.

Not necessarily - some things (like copper, for example) are extremely toxic to inverts like hermits without being (nearly as) toxic to fish.

I could try cutting open the hermit that is in the tank now,

Yeah, if you're confident it's either dead or a molt, I'd try opening it up and seeing if there's meat inside.

I’m using tap water that i have filtered with a reverse osmosis system,

Just to check, is it just a reverse osmosis (RO) system, or does it have a deionization (DI) setup too?

Here is a photo of the test

As a general rule, it's a good idea to avoid test strips and go with reputable single parameter tests (unless you're going with a high end automatic tester) - Salifert, Red Sea, and Hanna seem to be the big names for reputable tests.

Anyway, is this test strip meant for saltwater or freshwater? I ask because GH, Iron, and Nitrite aren't generally tested in saltwater, and Copper is really only tested when either medicating with copper or if there's a suspected problem. Also, Alkalinity in saltwater is typically just measured in dKH rather than as KH and TA.

Generally speaking, with saltwater, you want to test:
-Salinity
-Temperature
-Calcium
-Alkalinity
-Nitrate
-Phosphate
-pH

Suggested parameters for these can be found in the tables below:

Table 1. Parameters critical to control in reef aquaria.

Table 2. Other parameters in reef aquaria that aquarists may want to control.

here is what the crabs always do after a couple of days

Yeah, from what I've heard, it's fairly common for hermits to molt shortly after being put in a new tank, so I'd check for meat in there. Do you have anywhere in the tank where the remaining hermits could be hiding out if they're alive? Sometimes critters end up in weird places like the overflows and plumbing, not just in the rocks.

 

[Mr. Mojo Rising]

How new/old is your tank? Do they have enough food?

 

[Ndryden]

It's unlikely, but I'd say to set a camera to record the tank while you're not in the room and see if one of the clowns is going after the crab while you're not there.

Not necessarily - some things (like copper, for example) are extremely toxic to inverts like hermits without being (nearly as) toxic to fish.

Yeah, if you're confident it's either dead or a molt, I'd try opening it up and seeing if there's meat inside.

Just to check, is it just a reverse osmosis (RO) system, or does it have a deionization (DI) setup too?

As a general rule, it's a good idea to avoid test strips and go with reputable single parameter tests (unless you're going with a high end automatic tester) - Salifert, Red Sea, and Hanna seem to be the big names for reputable tests.

Anyway, is this test strip meant for saltwater or freshwater? I ask because GH, Iron, and Nitrite aren't generally tested in saltwater, and Copper is really only tested when either medicating with copper or if there's a suspected problem. Also, Alkalinity in saltwater is typically just measured in dKH rather than as KH and TA.

Generally speaking, with saltwater, you want to test:
-Salinity
-Temperature
-Calcium
-Alkalinity
-Nitrate
-Phosphate
-pH

Suggested parameters for these can be found in the tables below:


Yeah, from what I've heard, it's fairly common for hermits to molt shortly after being put in a new tank, so I'd check for meat in there. Do you have anywhere in the tank where the remaining hermits could be hiding out if they're alive? Sometimes critters end up in weird places like the overflows and plumbing, not just in the rocks.

Ok, i will try opening it up when i get home, yes it is RODI, the test strip says it’s both for salt and freshwater, but i will invest in some individual parameter testers, thank you for the advice, no not really, there would be 4 crabs hiding somewhere in the tank and the last two that did this was 2 weeks ago. I’ll update you here soon!

 

[Ndryden]

How new/old is your tank? Do they have enough food?

The tank is 3 months old, yes they have enough food, i use some long tweezers to set crab pellets right next to them and do it every morning, this along with whatever the clowns don’t eat and whatever algae they find i’d assume they have enough food

 

[ti_lavender]

Are there any other inverts? Do you see amphipods at night? That might help indicate a toxicity or not.