HCA: Hermit Crab Association

I apologize ahead of time for the lengthy post, but I think some background information is necessary to understand the situation.

For the last ~1.5 years, thanks almost entirely to this wonderful community, I have been providing my crabs with what I thought was good care. Now I am wondering if I'm actually doing something wrong. I'm hoping someone can offer some wisdom.

I have 2 problems:
1. one probably-dead crab
2. two always-underground, highly nocturnal, possibly lethargic crabs

When I first got the crabs I had them in a 10g tank that was not as hot or as humid as recommended. They spent part of their time above ground and part below, and they were active sometimes in the daytime, sometimes at night. Later I upgraded them to a 55g and improved the tank conditions. Soon after the upgrade 2 of them disappear (molting I assume) and a couple weeks later the 3rd follows suit. Eventually they return, I see fancy new black tips on their legs confirming they molted, and everyone is happy.

Soon after, the crabs start disappearing for longer and longer stretches until I assume they must be molting again. They also start spending less and less time above ground during the day. Eventually we stop seeing them at all except occasionally in the evening, though they must come out at night because food disappears.

This is now the pattern. I won't see a crab for a couple months, then I'll see them occasionally but only at night, then they disappear for a while again. Only 1 of the 3 crabs ever stays above ground during the daytime and he is the one I suspect is dead (I haven't seen him for ~6 months). With him missing, I haven't seen any of them above ground during the day in probably 8 months.

I didn't really worry about him too much because I have read on these forums that they can take 3 months to molt, and I've read of them doing 2 molts in a row, so I figured that was what was happening. Now I'm starting to think it's been too long even for that.

Of the 2 that remain, 1 comes out each night but never during the day. The other I haven't see in about a month. Before that he had just come up from a (presumed) molt, would come out at night for a couple weeks, then disappeared again.

When the crabs are out, they seem less active than accounts I read of other people's crabs. I have never had a problem with them trashing the tank. They dig some holes and move some moss and food around but that's about as destructive as it gets.

For a long time I took all of this behavior as a good sign - they are repeatedly molting, they must be happy and getting what they need and growing as fast as they can - now I don't know. I'm starting to think something is wrong that is making them overly nocturnal and lethargic.

Could I be doing something that is causing this, or do I just happen to have boring slowpoke crabs?

1. What kind of substrate is used in your tank and how deep is it?
Mix of beach sand, play sand, and EE. ~10 inches high, I don't remember exact mix, maybe 7:3 sand:EE?

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?
Almost in dead center of the non-substrate portion of the tank. Zoomed hygrotherm keeps the temp ~83 in the day and ~75 at night. Humidity stays around 75%.

3. Is a heat source used in the tank? If so, what?
Full length UTH on back of tank. Extends from top of tank down to 1-2 inches into substrate.

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)?
Fresh and salt water, both treated with "Prime" according to label instructions. Salt water made with Instant Ocean marine salt.

5. What kinds of food do you feed and how often is it replaced?
Combo of dried mixes from hermitcrabpatch.com and scraps of whatever fresh foods we humans are eating. Changed ~3 times/week.

6. How long have you had the crab and what species is it, if known?
Since Oct 2013, all PPs.

7. Has your crab molted, and how long ago did it happen?
Yes multiple times (I think), exact dates unknown. Two came up from molts within the last 3 months. Since I got them they've grown from shells approximately quarter size to approximately golf ball size.

8. What type of housing are the crabs kept in, what size is it and what kind of lid is on the housing?
55g glass aquarium. The lid is just glass laid on top of the tank with spaces for ventilation.

9. How many crabs are in the tank and about how large are they?
3 crabs, all similar sizes. Shell openings maybe around 1 inch? (~ golf ball size shells)

10. How many extra shells are usually kept in the tank, if any?
~15

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

12. How often do you clean the tank and how?
Never deep cleaned it, just spot clean anything I see.

13. Are sponges used in the water dish? If so, how are they cleaned?
Water dishes cleaned weekly with a scrub brush and vinegar (remove hard water), then rinsed. 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.)?
See main post.

16. Please describe the emergency situation in detail.
n/a

Hermit crabs are nocturnal by nature, and PPs tend to be less active.
Try getting some ecuadorian hermit crabs, they are more active.

I understand your concerns but I think there's a good chance nothing is really wrong. Your setup and conditions look great to me. Losing one crab to a bad molt over an extended period of time happens even under the best of conditions.

Unless there is a reason you'd prefer not to have more, I would definitely recommend increasing the size of your colony since you have plenty of space. Any species of crab would be fine, but the addition of a few more crabs will provide a lot of stimulation and socialization to your currrent crabs. One thing that has been made clear to me over my years of keeping crabs is that they have a very "monkey see, monkey do" behavior pattern. If one crab sees another eating, drinking, bathing, changing shells, exploring, adventuring, etc. they will often feel compelled to also engage in that behavior. So you don't need cram your tank full of more crabs, but a few additions could very likely make your crabs more active and get them out of the rut they're stuck in.

Your tank is beautiful, but if the decor has been in the same arrangement for a while you may want to think about changing things up, even in fairly minor ways. My personal advice is to add more plants. Put them everywhere. I really think they help give crabs a sense of security and adding plants to areas of the tank that aren't often trafficked can result in more interest and exploration of those areas.

If you're in the market for a budgetary splurge, you may want to consider a fogger. I bought one on a whim a while ago and some of my crabs really enjoy sitting in the mist and grooming.

I've always maintained a very nice crabitat but for many years my rugs and violas have been very shy. I never thought too much about it because they seemed to be normal and healthy. Over the winter I switched everyone to a new tank. It's a very similar size and I used a lot of the same materials, but for some reason my rugs and violas are now all outgoing superstars in the new environment. The behavior change doesn't really make sense, but I'm glad my crabs have responded so positively. Wish I knew specifically what it was that sparked this change.

Thanks for the responses and reassurances. I was sticking with 3 crabs because if they all grow to be huge I'm not sure there's room for more - this is probably as big of a tank as I want to have.

Rearranging the tank seems like a good idea. I've been wanting to do it, but was holding off because I'm likely to move soon and will necessarily have to do it again then anyway (and also dig around to see what happen to the missing crab). Maybe I'll do something more minor in the meantime.

I'm glad to hear your crabs changed attitudes, it means there's hope! Have they stayed outgoing for a long time in the new setup? Do you have before/after pics? Mine seemed to be excited and outgoing for a while after they moved into the larger tank but then it fizzled away. Maybe I should be renovating/rearranging on a regular basis to encourage exploring...

Is there any concern with the heater being the whole length of the tank?

Even if all your current crabs were jumbos, you'd still have room for more crabs in a 55. Some crabs grow quickly and some grow extremely slow so I wouldn't worry about having a tank full of jumbos anytime soon. There's no reason to be concerned about your heater setup.

I switched to the new tank in December and my rugs and violas have maintained their outgoing personalities since then with no sign of regressing.

My current 101 gallon



My old 90 shortly before the tank switch

Wow, those tree trunks are awesome! What are they?

Once I move and find out if Trundle is still alive down there I'll definitely consider getting more if the space is okay. Assuming they all survive into jumbohood, how many is reasonable in a 55g? I don't want to crowd them.

How big are your crabs?

Somewhere around the size of a golf ball I'd say. I've never put them on a sizing chart but I'd guess mediums?

Form wrote:Wow, those tree trunks are awesome! What are they?

All the wood in my current crabitat is cork.

Once I move and find out if Trundle is still alive down there I'll definitely consider getting more if the space is okay. Assuming they all survive into jumbohood, how many is reasonable in a 55g? I don't want to crowd them.

I go by the guidelines that were in place here at the HCA when I started crabbing so I count jumbos as needing about 5 gallons of space each. My jumbos have always done well with that but I think they keep raising the guidelines so I don't know what the rec is now. To a large extent, how many crab you keep in your crabitat depends on your preferences and the makeup of your colony.

According to this you could get a few more hermit crabs.

StarWarsHermitCrab wrote:According to this you could get a few more hermit crabs.

Just wanted to add the link to the article for Tapatalk users. It only shows up as the picture for me.
viewtopic.php?f=26&t=92541

HCADirectors wrote:Please note that the above is only a guide. Every hermit crab will get along with other hermit crabs and adjust to captivity differently. Some Es and Exotics may be too crowded by this guideline, while Purple Pinchers are normally fine with being more crowded. Enclosures that are over 55 gallons should be capable of supporting more hermit crabs then this list suggests. It's up to you to pay attention to all of your individual crabs needs and wants. Remember that hermit crabs can grow quickly and you should take into consideration the amount of space they'll require over time. Please adjust your tank size and hermit crab numbers according to your situation. Aquariums that are "tall" generally support less crabs than those that are "long" or "breeder". These guidelines are minimum recommendations, and hermit crabs may do better with more space per crab and with deeper substrate depth then what is stated here.

Right on cue, the one crab that was coming out at night to eat has gone down again. :roll:

I'm glad I'm not doing anything grievously wrong. That being the case, I think my plan will be to:
1. rearrange the 'tat, lowering the substrate on one side and filling the space with more climbing areas and adding additional plants
2. read up on some of the more active species and consider adding 2-3 of them


Any suggestions for #2? The things I'm looking for would be:
- active, at least sometimes during the day
- low to medium difficulty (I know some species are particularly hard to keep alive and healthy)
- agreeable with my current PPs