Lots of empty shells!?! Help please!

EricksonHQI · Jul 2, 2012

I have had my biocube up for about two months. I have had countless crab loss. I was always hoping it wasn't lack of food. When they die they have abandoned their shells. We always find the dead bodies. Their shells have stayed abandoned. Never gets taken by another crab. My corals don't get picked at. And typically doesn't happen to my snails. Till this evening when I noticed a nassarius snail. I have over 35+ shells in the aquarium, 20 of them I bought empty. Crabs only switch to the ones I bought. Will not take the dead ones.... What is happening. Any ideas?

BarbH · Jul 2, 2012

My guess is that the shells may be too small for them or there could be other reasons. At times I have seen my crabs change shells from day to day part of it is I think they are looking for one that is a good fit, that along with hermits will be hermits.

uall8up · Jul 2, 2012

Did you go through a complete cycle before adding them?

droblack · Jul 2, 2012

You likely have a predator. Probably a crab or mantis shrimp. Get a flashlight and cover with red plastic or red balloon and do a night dive into your tank and see what is lurking after hours.

Steelerfan747 · Jul 2, 2012

droblack said:
You likely have a predator. Probably a crab or mantis shrimp. Get a flashlight and cover with red plastic or red balloon and do a night dive into your tank and see what is lurking after hours.

+1 on the mantis. I had one in my tank and would find hermit bodies from time to time. Do you ever hear snapping noises from the tank?

EricksonHQI · Jul 2, 2012

I thought it may bea preditor as well... No snapping comes from the tank. I've done night time searches and have only seen one thing that looks weird it is a very brightly orange centipede looking worm. If it a crab it would have to be a bigger one right? I have seen no crabs....

EricksonHQI · Jul 2, 2012

My tank is completly cycled...

EricksonHQI · Jul 2, 2012

I have done daily tests to make sure my tank is not going through any cycles. Also had LFS done tests three times a week. We come up with the same params...

Loki · Jul 2, 2012

Let's get a good background. Did you start with live rock or dry? If live where did it come from?

Sand live or dry? If live from where?

How many shrimp did you put in? What kind?

How many hermit crabs? What kind?

Any other crabs/clean up crew?

I have never (until this tank) been able to keep a CUC alive for more than a month or so.

It seems that your question is why aren't the crabs switching into the shells from dead snails/ other crabs. Is this correct?

EricksonHQI · Jul 2, 2012

Loki2902 said:
Let's get a good background. Did you start with live rock or dry? If live where did it come from?

Sand live or dry? If live from where?

How many shrimp did you put in? What kind?

How many hermit crabs? What kind?

Any other crabs/clean up crew?

I have never (until this tank) been able to keep a CUC alive for more than a month or so.

It seems that your question is why aren't the crabs switching into the shells from dead snails/ other crabs. Is this correct?

Not quite.. My main question is why are all my crabs dying? I have had over 11 die now and a nassarius snail...

We started with 30 pounds of cured fiji live rock
20 pounds bio-active live sand.
We temporarily had a peppermint shrimp in our tank to take care of our aiptasia problem, but he is gone now.
We started with 12 blue leg hermits, added 10 more down the line due to excessive algae.
Our other clean up crew now includes:
- 3 nassarius snails
- 2 astraea snails, ? photo | Flickr - Photo Sharing!
- 1 big turbo snail

Other tank inhabitants are 1 o.clown, 1 royal gramma, frogspawn, moon coral, mushrooms, and button polyps

Loki · Jul 2, 2012

It may be that the tank is to young to have that many crabs in it. But if you are feeding the tank they would get food from that and not die. So that leaves water quality or predators. Was the tank new when you set it up? Is there a chance that it was used before with copper? Was your tank completely cycled when you added the CUC?

As stated above others could be a predator in the tank. It is possible with the live rock. When looking at the tank at night it is best to use a red light to not disturb what is happening. You can put a red ballon over a flashlight to make a red light.

In my last two tanks I couldn't keep a clean up crew. I wish I could tell you why mine would always die to help, but I never figured it out.

ritter6788 · Jul 2, 2012

Don't blame a mantis until you find BROKEN shells. Very easy to hear and spot. Mantis shrimp are not secretive killers. If you have one you will know it.

EricksonHQI · Jul 3, 2012

Loki2902 said:
It may be that the tank is to young to have that many crabs in it. But if you are feeding the tank they would get food from that and not die. So that leaves water quality or predators. Was the tank new when you set it up? Is there a chance that it was used before with copper? Was your tank completely cycled when you added the CUC?

As stated above others could be a predator in the tank. It is possible with the live rock. When looking at the tank at night it is best to use a red light to not disturb what is happening. You can put a red ballon over a flashlight to make a red light.

In my last two tanks I couldn't keep a clean up crew. I wish I could tell you why mine would always die to help, but I never figured it out.

We are feeding the fish once a day with brine shrimp, so I know the hermits are also finding things to eat.

All our parameters are good. I do tests every couple days and in the beginning we were also having the tests done at our LFS 3 times a week, they matched our results..

pH : 8.2 or 8.3
Nitrates: 0
Phosphates: 0
Calcium: 460
KH: 11
Hydrometer reads: 1.025

The tank was new when we setting up. And yes our tank was fully cycled before we added our cuc

Loki · Jul 3, 2012

everything seems to be just fine.

I just thought of this. This is the first time I am using an RODI unit, and its the first time I have had success with my CUC. are you using RODI water? I don't know if that would/could cause it but it may be worth looking at.

Chameleon · Jul 3, 2012

Don't rule out unknown crustacean pathogen. Maybe they are catching a cold or getting hermit smallpox...

Chameleon · Jul 3, 2012

But I be it is something water chemistry related as Loki suggested...just throwing out other possibilities

EricksonHQI · Jul 3, 2012

We buy our saltwater already made from our LFS. We do use RO water for our top offs. I don't trust tap water.

EricksonHQI · Jul 3, 2012

We find the dead crabs out of their shells,
photo | Flickr - Photo Sharing!
What wold take hermits out of their shells or cause them to leave their shells like that?
Then the shells stay empty, the crabs will only switch with the ones I have bought... I. Just baffled!