HCA: Hermit Crab Association

I have three tanks (20 gallon for general population, one for new recruits and another for molters) and its fall now and my tank is by the drafty area by the hall to the door and that's the only place for them. It's been a constant battle with the heat in the big 20 gallon for about a week now so I bought a $50 heater and that helps get it up to 70°F but then the humidity is at 99%. I figure I'd sacrifice the high humidity for a warmer tank and idk if that's okay?? It gets 12°F outside at night and it's not full blown winter yet. Help!
Plus side my hermits are more active than they've ever been.


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I would definitely try to get it warmer. A tank in the 60's is dangerous to your crabs. Ideally, you want the tank around 80F. You can add another heater or try to insulate your tank to keep heat from escaping. I have to use things like styrafoam, aluminum foil, and cardboard during power outages to keep the tank warm.

There lots of things you can do to lower humidity, although most of us struggle with the opposite problem. You can move your water bowls to the side of the tank opposite the heaters to slow down evaporation. Many people have found that heat lamp lower the humidity in the tank and help dry it out, so that could help both of your problems.

Thanks. I have a towel over the ISO and secondary newbie ISO tank, that's helping is stay around 70°-72° It's hard to keep it warm when they are so close to the foundation during freezing weather like it has been this fall. I will look into the heat lamp. What wattage should I use for a 2.5 gallon and a 20 gallon?


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Also I have another emergency if anyone can help. One of my teenie hermits, Willow, has lost a leg and big claw. I'm not sure how it happened but I'm keeping her in ISO with 70° heat (idk the humidity I have yet to buy one for this tank but it has condensation) it has mixed Eco earth and crabitat sand in it about 3" high. Also, powdered meal worms and powdered almonds in the food dish along with a soaking bowl and sponge. I dug a little hole with my finger and put her in there. Am I doing everything right? Is she possibly molting? Her color is the same orange and she doesn't like to move around but she moves inside her shell.


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Dropping limbs is a sign of stress or improper conditions. Are you absolutely sure that tank has stayed warm enough? 75 degrees is the lowest people recommend going. 60s can kill. I had a power outage and one of my tanks (I only have one now, though) dropped to the 60s for 3 days and the crab in the tank dropped a leg and ended up dying. If your crab is dropping legs, make sure you feed high energy foods like honey and sweet fruit, with plenty of protein and calcium. If she molts, she'll need the protein and calcium and honey will help give her some energy if she's lethargic. Sponges harbor bacteria and most crabbers don't recommend using them at all, or cleaning them daily if you do use them. A normal molt does not involve dropping legs separately. Normal molts have the exo come off in one big piece, usually still intact.

About heating the 20g, when I used a 20g, I needed two big heat mats on the sides and a 50watt heat lamp to keep it warm. Insulating with tin foil helped. I never got to try styrofoam for insulation but people highly recommend it. I had a harder time heating the 20g than I've had with heating a 10g, 29g, or 50g. It was insane.

I did a deep clean in the ISO that she's in with brand new EE, clean fresh water and fresh food. She's still moving inside her shell but not going anywhere else. I have a heater along the whole bottom and even with styrofoam and a microwaved towel and rice bag covering it (I gotta re-heat them about every three hours or so) it's only 74°. Could it be my thermometer? I got a strip on the outside that glows green/brown/blue around the temperature. Should it be closer to the dirt inside or lower on the tank?


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kornchaser wrote:I have a heater along the whole bottom and even with styrofoam and a microwaved towel and rice bag covering it


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Confused lol. Do you mean you have the heater on the bottom of the tank (underneath it) or along the bottom on the backside of the tank? Either way the heater needs to be on the backside of the tank above the substrate line to benefit the crabs. Heaters aren't meant to get through that much sub and can become a fire hazard if left like that!


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1. What kind of substrate is used in your tank and how deep is it?
A: Both my 2.5g ISO and 20g main have EcoEarth. The 2.5 has about two inches and the 20g has about 4"

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?
A: in my 20g I have a hygrometer that usually reads 99% and a strip thermometer that's been reading 76°. I only have a strip thermometer on the outside of that tank on my 2.5g that usually reads 74°-78° depending how warm the towel is I've been wrapping around it.

3. Is a heat source used in the tank? If so, what?
A: Both tanks have a uth that covers about 2/3 of the bottom of the tank on each and the backs and sides are covered in styrofoam.

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)?
A: in the 20g there is both salt and fresh that get changed out every few days. In the ISO I switch back and forth between salt and fresh because the lagoon takes up so much space which I'm planning on changing soon. I use All Living Things water conditioner (4 drops to 8 fluid oz) and soaking salt (1 teaspoon to one cup water)

5. What kinds of food do you feed and how often is it replaced?
A: powdered meal worm and pellets for the small crabs with whole for the bigger crabs, it gets changed out every few days. Sometimes I add spinach and raspberries which gets changed out the following day. I'm currently looking into buying some cuttlebone and having my grandma dehydrate some veggies for them (carrots & celery) I also feed them powdered almonds from time to time.

6. How long have you had the crab and what species is it, if known?
A: Willow has been with me since 9/17/2014 and she is a teenie purple pincher (all my crabs are PP)
7. What type of housing are the crabs kept in, what size is it and what kind of lid is on the housing?
A: There's six in the 20 gallon long 30L 12W 12H and two teenies currently in my only ISO: Pepper which is new so she's pinchy and likes to hide and burry herself and the affected crab, Willow. There's a glass canopy over the 2.5 gallon and a mesh screen over the 20 gallon covered by styrofoam.

8. How many crabs are in the tank and about how large are they?
A: 2 teenies in the 2.5g (.5-.75") and 6 in the 20g.
Octavius: (biggest) 3.5"
Matty: 1.5"
Junior: (molting) 2"
Kaylee: (smallest) .5"
Kita: .75"
Bruiser: not entirely sure, he's outgrown his shell and his BP is about 1.13" which is bigger than my smallest crabs

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

About 11 in the big tank and currently one in the small tank

10. Have there been any fumes or chemicals near the crabitat recently? None

11. How often do you clean the tank and how?
Change out dry food every few days and fresh food the following day. Water dishes get cleaned and refilled whenever there's too much dirt in there so about every other day.

12.Are sponges used in the water dish? If so, how are they cleaned?
I bought a whole bag of about 6 natural sea sponges that I cut and sized to my liking and every time I clean out the water dishes I rinse out the old sponge and get all the poop and dirt out of it then let sit out to dry and microwave it for a minute once it's dry. I use one already cleaned and sanitized to replace the sponge.

13. Has anything new been added to your crabitat recently?

Yes everything's new and plastic because I always get mold on anything wood in there, this was about a month ago. They all seem to like it. The warm cave and mushroom log to climb in and lagoon soaking bowl are all new, i rinsed them all clean before I added them to the crabitat.

14. 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.)?

I like to wipe down the condensation off the inside of the glass with a plain dry wash cloth. I empty the dirt from shells all the time and like to just sit in front of my crabitat and research for hours so I know what kind of shells they like and what not.

15. Please describe the emergency situation in detail.
A: I found Willow tucked under some wood pieces (little climbing toys) with her claw and leg strewn about from the water dish to the wood. I picked her up and she was moving so i ISO her and check on her every day. I pick her up and blow lightly into her shell seeing if she responds which she has been for a bit now. Should I put her in the food? She doesn't move around and she needs to eat. Should I not pick her up at all? Is it possible she was in a fight or simply stressed?


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I moved the heaters so that they're along the back now, I didn't know oops


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moonbeam wrote: Confused lol. Do you mean you have the heater on the bottom of the tank (underneath it) or along the bottom on the backside of the tank? Either way the heater needs to be on the backside of the tank above the substrate line to benefit the crabs. Heaters aren't meant to get through that much sub and can become a fire hazard if left like that!


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I moved my heaters so that they are along the back of the tanks, I didn't realize that was a fire hazard. Also that explains the high humidity in both my tanks. Also does anyone have any good sites for a background for my aquariums? I can't find any the right size and honestly a little weary about buying them from Amazon since some say "reduced to $15 from $1,000".


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Also if it's a "under tank heater" then why is it not, in fact, supposed to be “under the tank”?


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Ok a few things to go over, I'll do them by number of the thing you filled out.

1. The recommended amount of substrate is 3 times your tallest crab or 6 inches, whichever is taller. 2-4 inches isn't enough for your crabs to be able to molt safely.

2/3. 76 is on the low end of what is safe for pps. Ideally your heat and humidity should both be around 80. I have never used a strip thermometer but I'm guessing it wont give you an accurate reading unless it's inside the tank it's self. Someone chime in if that's incorrect. Once you move your heaters and thermometer I think your heat will rise and if not you'll be able to tell so you can fix it. I think I read that you already moved the heaters to the backsides of your tanks above the substrate lines?

4. Both salt and fresh need to offered at all times. The all living things conditioner isn't that great. There are other brands sold for fish which are more efficient and better for your crabs. Also, marine salt (like for fish tanks as well) such as instant ocean is also better for your crabs. Other salts lack the nutrients that crabs need to remain healthy.

5. Check your commercial pellets to the safe foods list. Most are not good for crabs. Fresh foods are great and most of the time you can share whatever you're having for dinner with the crabs. I usually save a piece of meat, fruit, or veg on the side and cook it plain (no seasoning or salt) and put it in their fresh food dish. I'll link the fresh foods list and another thread on foods in a few minutes.

6/7/8. Six crabs is the max I would put in a 20g. The absolute minimum tank recommended to keep pps in is 10 gallons. The 2.5 is going to get very cramped very fast. I would maybe look on Craigslist for a larger tank where you could keep all of your crabs and maybe use your 20g for an iso. You can usually find good deals on tanks there.

9. It's recommended to have about 2-5 shells per crab. They need some slightly small, roughly the same size and slightly bigger offered. I have 6 crabs in my tank right now and about 20-30shells for them to look at. I have (over time) collected extras so that I can change them up and offer different shells every once in a while.

12. I don't use sponges just because of the maintenance required to keep them clean of bacteria build ups. In the future you may wanna consider using moss pits as an alternative? I think they require less cleaning, provide great boosts in humidity and my crabs love the moss pits. Regardless of anything else in my tank, the moss pit gets used every single day by one crab or more. But it does sound like you're cleaning your sponges correctly (if someone disagrees please chime in, I could be wrong).

14. I don't know if this has any validity but I use paper towels to clean my glass. It's important not to use soap and I've always worried that any soap residue/laundry detergent will effect my crabs. I have no clue if it's true, maybe just my over protectiveness coming out lol.

15. It's very likely stress. If I remember reading correctly she's in a 2.5g right? When conditions aren't optimal crabs can very easily become stressed and can suffer from pps which can kill them. I guess a fight is also possible since it may be a bit crowded in there but I think stress is more likely. She definitely needs to be left alone. No more taking her out, picking her up. She needs sometime to destress and possibly gear up to molt. I'd offer her an iso with a hit or hide for darkness, fresh and salt water, and food like protein, calcium and something high energy like organic honey, peanut butter, or bee pollen. And give her some time. Picking her up to check on her will only add to her stress. If she passes you will know from the smell.

About the backgrounds, I have no clue where to find one but I do agree that a mark down from 1,000 to 15 is something to be weary of.

Under tank heaters are meant for reptiles. They usually do go under the tank in those cases because reptiles don't require near as much substrate as crabs do. The UTH can actually hear their tanks from the bottom up, not the case with crabs. It's kinda crazy but most of the stuff offered for hermit crabs is not good for crabs so over the years crabbers have come up with other things that work better for crabs. Just most aren't actually designed for them lol.

Hope all of this helps, let us know if you have any other questions we can help you out with and please give us updates on willow!


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Edit to add: these are the safe food links
viewtopic.php?t=92557#p852660
viewtopic.php?t=92554#p852657

This is the commercial food link so you can compare yours to it. viewtopic.php?t=92555#p852658