Murderous Crab?

[Mtyree]

Hi, I have had hermit crabs for about 6 months now, i started with a medium sized and a smaller sized set of crabs purchased from PetCo. After one day the smallest died and he was replaced within a day so my big crab wouldn't be lonely. This crab was still smaller than the larger one and he was very active and they seemed to get along very well, until I woke up one day and he was dead. I then got a crab almost identical to my large one, they have gotten along great for months. However in the last few days they started acting strange, my original crab stole the other's shell and I figured they just swapped, til two days later when I found my organs crab had ripped the other out of his shell. I followed advice on this forum and was able to get him back into a shell, however at some point today he died. My original crab, is perfectly heathy as far as I can tell. I keep the tank conditions stable, and they have plenty of space and substrate. I cannot figure out what is going on. I am worried that my original crab is killing all of these crabs, I don't want him to be alone, but I also don't want him to keep killing. I understand that this just happens, but after multiple incidents I am worried. Should I bring home another crab? Is it possible he is a solitary type of crab? Would having more than two crabs help? I really am at a lose on what to do,so any advice is appreciated!

1. What kind of substrate is used in your tank and how deep is it?
A mixture of Eco Earth coconut fiber substrate and plain playground sand. It varies between 4-8 inches in depth around the tank, deepest in the area were the crabs spend most of their time

2. Do you have gauges in the tank to measure temperature and humidity? If so, where are they located and what temperature and humidity do they usually read?
There is a dual humidity and temperature gauge at substrate level on the end with the heat source.This usually reads between 70% -80% humidity and 75 -80 degrees. I also use a hand held infrared heat gun to monitor the tank.

3. Is a heat source used in the tank? If so, what?
Right now it is a single bulb system with a 40 watt moon bulb.

4. What types of water are available (fresh or salt) and how is the water treated (what brands of dechlorinator or salt mix and what ratio is used to mix it)?
I use Instantocean to make the salt water, I mix large batches using the instructions on the box. I have a reverse osmosis system in my house which removes chlorine.

5. What kinds of food do you feed and how often is it replaced?
A rotating mixture of fruits, veggies, popcorn, sea weed, chicken, shrimp, and a few other things. These are changed daily or every other day.

6. How long have you had the crab and what species is it, if known?
I have had the one six months and I am not sure on his species. The one that died I had 3 months and he was a purple pincer.

7. Has your crab molted, and how long ago did it happen?
None of them have ever molted.

8. What type of housing are the crabs kept in, what size is it and what kind of lid is on the housing?
30 gallon tank, with a screen lid covered in saran wrap.

9. How many crabs are in the tank and about how large are they?
I usually keep two they are medium to large, and are about as big as the palm of my hand.

10. How many extra shells are usually kept in the tank, if any?
3

11. Have there been any fumes or chemicals near the crabitat recently?
Not that I am aware of

12. How often do you clean the tank and how?
I had to bake the sand once, their toys get washed monthly, other than that I spot clean.

13. Are sponges used in the water dish? If so, how are they cleaned?
No sponges

14. Has anything new been added to your crabitat recently?
No

15. Is there any other information you would like to share that might be helpful (anything that is regularly part of your crab care, playtime, bathing, etc.)?
The original crab is highly active and likes to be handled. While the one that died was highly aggressive and active when I got him with in a few weeks he became quite anti social and it was very rare for me to see him.

[soilentgringa]

Hi. Please fill out the emergency template so we can help you address this issue.

Copy and paste these questions in the comments below with your answers. Be specific with brand names, etc. as much as you can.

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http://www.hermitcrabassociation.com/ph ... hp?t=46102

[Mtyree]

Do I need to move this post to Emergency?

[CallaLily]

It is recommended you offer a minimum of 3 extra shells per crab, in appropriate sizes and types. More is better. Preferred Shell Guide. This could very well be the main issue.

Also, it's my experience that sloping substrate can lead to problems. They don't always dig in the deeper area. Best to have the proper depth for your size crabs all the way across. Or at least no part shallower than the minimum recommended. The reason for deep substrate is to provide protection during molting. They're very vulnerable during this time, and too shallow substrate can make it easier for other crabs to stumble across them and take advantage.

Are you sure they haven't molted? I would expect the one you've had longest to need to molt soon, if he's medium sized? Sometimes they're sort of half crazed for food and shells when they're first brought home up until they successfully molt with you. I think I might wait for him to molt, then try reintroducing another crab. Meanwhile you can have the new crab isolated and getting his fill and hopefully molt before too.

Personally I find it's more common to have problems between similarly sized crabs. Maybe try to get a crab that's larger than this guy?

Were the first two deaths obvious attacks too or maybe PPS?

[Mtyree]

Thank you for your reply. I think that shells are a large part of it. I've ordered more and plan on stalking up before I get any more crabs. As far as molting goes the longest I've gone with out seeing this crab is 5 days. And he showed no signs of molting. Would getting more than one other crab help, to relive the tensions?

[CallaLily]

You could certainly fit more than 2 crabs in a 30 gallon tank. And if nothing else, it would at least spread out the possible bullying so it isn't just one crab constantly picked on. But I don't know for sure if it'll make a difference. The only time I've only had 2 crabs was the first few days I started crabbing back in '08. We added to our crew pretty quickly.

[Mtyree]

Alright thank you so much for your help!! I am gonna start with what you said and go from there. I think having at least three would help a lot and all of your other ideas seem really good to me. Again thank you so much, this has been driving me crazy!