HCA: Hermit Crab Association

Hello!

We welcomed three small purple pinchers in December 2023. The 30 gallon long tank has 6” of substrate which is a 50/50 mix of play sand and coconut substrate. I have 15 shells in the tank, salt and fresh water (with ramps and deep enough to submerge). I have 75-80% humidity and a heating pad on the back of the tank (surface level) that is programmed for 80 degrees. The tank is at 75 degrees.

All three crabs were active for the first 2 weeks. Since then 2 of 3 crabs have been underground since late December (3 months ago). The third crab went under ground about 6 weeks ago. One of the crabs who went underground in December, resurfaced two weeks ago for about 4 days. He looked newly molted but with a hard shell. He ate, drank, bathed, moved all the shells, then tunneled again and has been gone for another 2 weeks.

I have been replacing food every two days and water weekly. There is no activity at night. There is no smell. What am I doing wrong?? Do little crabs molt for more than 3 months? Why did the newly molted crab disappear again? Conditions do not seem to be stressful. No fighting among crabs. One of the crabs switched shells just prior to tunneling in December, otherwise no shells changes. I do not want to dig them up but I am worried they are not okay (or that they hate me).

Any insight is welcomed!

The fact that one of the three-monthers came back up means they may not be dead. Even large crabs seldom molt that long but they may just prefer it underground, especially if they’re new and not used to the tank yet. What do you have for cover (hides, plants, etc.)? Hermit crabs tend to be more active above ground if they’re not in the open all the time


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I have two half coconuts, two climbing logs, and a moss covered climbing stick structure. I have some moss as well that the crabs piled up. Do you have suggestions for plants or other hiding places?

Looking for more feedback! I ended up digging through the substrate and found all three crabs (since they have been down there so long and you noted they shouldn’t molt that long, I hoped I was not going to disturb the molting process and assumed they were dead). All three look happy and healthy! They all do look like they have molted due to brighter colors. They moved around their space (I got more plants for additional hiding spaces as per your suggestion). And within a day, two of the three have re-buried. What am I doing wrong? I’m happy if they are happy tunneling and underground but they are not re-surfacing at night (I raked the sand so I could tell if they popped up for food, water, or a tub). I am concerned about eating, drinking, etc.

Thank you for any insight you can provide.

Answers for context:

1. What kind of substrate is used in your tank and how deep is it? 50% play sand, 50% substrate, 6” deep

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? Yes, back of tank. 75-85% humidity, 72-78 degrees.

3. Is a heat source used in the tank? If so, what? Yes. Heating pad along back at surface level set to 80 degrees with temperature gauge.

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. Both in tubs that are deep enough to submerge with ramps. 1 tspn of salt mixture per 1 cup water. Prime as dechlorinator.

5. What kinds of food do you feed and how often is it replaced? Pellets or variety food (Flukes) changed every 3 days. Fresh food (red peppers, coconut flakes) changed every day. Cuttlefish bone.

6. How long have you had the crab and what species is it, if known? Purple pinchers purchased December 2023z

7. Has your crab molted, and how long ago did it happen?
Based on digging them up this weekend (after initial
Post) all three have molted within the last 3 months.

8. What type of housing are the crabs kept in, what size is it and what kind of lid is on the housing? 20 gallon long tank. Hinged solid lid.

9. How many crabs are in the tank and about how large are they? 3 small crabs all equivalent sizes.

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

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

12. How often do you clean the tank and how? Not yet. Though water is changed weekly, and 2x daily spritzing.

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

14. Has anything new been added to your crabitat recently? Added artificial plant per suggestions for additional hiding spots.

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.)? No

16. Please describe the emergency situation in detail. 3 crabs buried for 3 months after purchase. After digging up this weekend, all are happy and healthy, though two almost immediately reburied.

1. What kind of substrate is used in your tank and how deep is it? 50% play sand, 50% substrate, 6” deep

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? Yes, back of tank. 75-85% humidity, 72-78 degrees.

3. Is a heat source used in the tank? If so, what? Yes. Heating pad along back at surface level set to 80 degrees with temperature gauge.

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. Both in tubs that are deep enough to submerge with ramps. 1 tspn of salt mixture per 1 cup water. Prime as dechlorinator.
Curly - Check the 'water' care sheet... Are you using Instant Ocean, or a different brand of marine salt? The correct amount of salt is 1 Tablespoon in 2 cups of water.

5. What kinds of food do you feed and how often is it replaced? Pellets or variety food (Flukes) changed every 3 days. Fresh food (red peppers, coconut flakes) changed every day. Cuttlefish bone.
Curly - Pellets are generally not great long term, since many of them contain preservatives. Be sure that you are feeding a varied diet, including animal protein and calcium daily. Be sure to check out the Nutrition care sheet for full info.

6. How long have you had the crab and what species is it, if known? Purple pinchers purchased December 2023z

7. Has your crab molted, and how long ago did it happen?
Based on digging them up this weekend (after initial
Post) all three have molted within the last 3 months.

8. What type of housing are the crabs kept in, what size is it and what kind of lid is on the housing? 20 gallon long tank. Hinged solid lid.

9. How many crabs are in the tank and about how large are they? 3 small crabs all equivalent sizes.

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

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

12. How often do you clean the tank and how? Not yet. Though water is changed weekly, and 2x daily spritzing.

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

14. Has anything new been added to your crabitat recently? Added artificial plant per suggestions for additional hiding spots.

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.)? No

16. Please describe the emergency situation in detail. 3 crabs buried for 3 months after purchase. After digging up this weekend, all are happy and healthy, though two almost immediately reburied.
Curly - Stop digging up your crabs. Seriously, they know what they are doing, and obviously wanted to be down there, since they went back down as soon as they were able. Joe said they likely won't molt that long, but that they might just be hanging out underground. But since you don't know when they started molting, it is always best to NOT dig them up. I mean, if they are dead, you gain nothing by digging for them. But if they are molting, you can cause damage that they may not be able to recover from. Crabs will come up and eat and drink when they need to.