Cannibalistic crab (?) & mites

[reichnat000]

I currently own 11 crabs in a 125 gallon tank that are small/medium in size. (I've kept this colony for about a year) All of my crabs were surfaced except 4 that were in isolation tanks, and I noticed one of my crabs left his shell and didn't pick up another ( I keep count in case of things like this), so I dug up all of my sand and couldn't find him! It's impossible for an escape in my tank so now I'm wondering if one of my other crabs ate him? Do they do that?
Another problem I'm having is that one of my crabs has little red bugs crawling on him. I've dealt with other mites but I've never seen red ones so I'm wondering if they actually are mites.(They seem to only be on the one) I have him in an isolation tank and I'm bathing him and cleaning the tank out, but it's been over a week and they are still there. Is there something else I can be doing? His skin is also very pink, though he hasn't molted in about 2 months so I'm a little concerned about him.
I'm at proper humidity and temperature in my tank(s) and my substrate is about 6-8 inches deep if that means anything.

[JulesRolyCrab]

A crab without a shell is very, very weak and yes, could have been attacked for his shell. They can be cannibalistic as well, and I am sorry that you couldn't him during the dig.

Here is the Emergency template to help us help you and determine anything that could have contributed to the problems:
viewtopic.php?f=27&t=46102

Also for the mites, could you post a picture? What is the species of the attacked crab? Red mites are actually harmful to the crab, unlike other types, I would immediately ISO the crab to prevent infecting the entire tank! This is from the mites page:

The other type of crab mite is slower moving and more stationary. These glue themselves to any soft part of the crab such as the eyes or joints or mouthparts. They are most commonly found on Strawberry hermit crabs, and on other exotics but can infest any species. They are white, cream, grey, pink, or red in color. They don't appear to have long legs and are shaped more like a tick.
If a new crab has mites and you have not had him anywhere near your current crabs, then you should set up a bare-bones ISO -plastic hide and paper towels for "substrate" - far away from your current tank so that you can bathe the hermit crab and clean the tank on a daily basis to remove the mites before they spread. Details on Mite Baths is farther down.

If the tank is infested, there is more about that in the page below.
Mites: viewtopic.php?f=67&t=92530
Posting pictures: viewtopic.php?f=8&t=87783

[reichnat000]

Thank you for replying!

1. What kind of substrate is used in your tank and how deep is it? Play sand mixed with a little coconut fiber

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? I have 4 on different parts of the tank and they usually read 78-79 degrees and the humidity is 78

3. Is a heat source used in the tank? If so, what? 2 UTH, one on the side of the tank above the sand and one on the side touching air and sand.

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)? Both salt and fresh in large but not too deep dishes, I use Aquasafe from Tetra and Zoo Med salt water mix

5. What kinds of food do you feed and how often is it replaced? I feed different kinds of vegetables and fruits, cuttlebone, dried crustaceans, and sometimes cooked eggs. I feed right before bed and replace it right when I wake up.

6. How long have you had the crab and what species is it, if known? I've owned these crabs for over a year and they are Purple Pinchers

7. Has your crab molted, and how long ago did it happen? He molted a little over a month ago

8. What type of housing are the crabs kept in, what size is it and what kind of lid is on the housing? 125 gallon tank with a half mesh and half glass lid with screen locks

9. How many crabs are in the tank and about how large are they? 11 crabs and are small-medium

10. How many extra shells are usually kept in the tank, if any? 34 extra shells

11. Have there been any fumes or chemicals near the crabitat recently? No

12. How often do you clean the tank and how? I deep clean every 2-3 months. I take all of the sand out and wipe down the tank with water, wash toys and shells, and then get new sand and put it in. I clean out water and food dishes everyday and do spot cleaning every day too

13. Are sponges used in the water dish? If so, how are they cleaned? I don't use 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.)?

16. Please describe the emergency situation in detail.

[soilentgringa]

Hi,

A couple of things that stand out to me are:

The salt water treatment you're using isn't really adequate for hermit crabs. Unfortunately almost anything marketed towards hermit crabs is useless. Most of us use Instant Ocean just because it's easy to find and cost effective. 1/2 a cup per gallon of water will last a while if you just have one tank.

If your conditions are stable and your substrate is a good mix of playsand and eco earth, it is not necessary to remove substrate at all. Beneficial bacteria and microbes build up over time to help break down waste and add to the over all health of the crabitat. Removing the sub can stress crabs out and you can also risk digging up molters or crabs that have buried to destress.

If you can post pics of the mites that would be awesome. Unless you see them attached to the joints and eyestalks of your crabs, they are probably harmless food mites.

May I ask why you have crabs isolated in different tanks? It is not necessary to isolate molting crabs, this is sortof an outdated concept. It's best to let them do what they do naturally and allow them to dig. A 125 gallon tank is PLENTY of room for 11-15 crabs as long as your colony is getting along and they aren't all jumbos (softball sized).

I hope we can help you get this sorted out.