Why is my crab taking so long to molt?

[Rae_K]

I have two Caribbean hermit crabs, one is about 5 years old and the other is about a year and a half. The younger crab originally never gave any signs that he was about to molt so when I picked him up one day, one of his legs fell off. He wasn’t really moving otherwise and was on the surface in the middle of the tank, so I picked him up and put him to the side of the tank so he wouldn’t be trampled. He has been moulting since April 25. I’ve been picking him up these past few weeks and he stays firmly in his shell. He doesn’t smell like fish either. I’m not sure why he has been moulting for so long. I’m not sure if his leg falling off has anything to do with it. He is also on the opposite side of the tank as the heat mat so I’m not sure if I should move him closer to it. I’m really worried because my previous crab died half way through her molt and I’m not sure why so I’m scared that will happen again. If anyone has any ideas, that would be great!

[curlysister]

Has the crab shed it's exoskeleton and eaten it?

Crabs should bury themselves under the substrate to molt, so something may not be ideal in your tank. If you copy and paste the 'emergency template', and answer the questions, we can help trouble shoot.

[Rae_K]

1. What kind of substrate is used in your tank and how deep is it?
I have 3 inches of Calcium sand and Soil mix and a third of the tank also has another 3 inches of reptile moss.

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?
The hydrometer is on the right side of the tank and reads 75% humidity during the day and 40% humidity at night. the thermometer is on the left side of the tank and reads between 24 and 28 degrees Celsius.

3. Is a heat source used in the tank? If so, what?
There is a reptile heat pad under the mossy portion of the tank.

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)?
There is one bowl of distilled water (water is distilled through boiling) and one saltwater bowl. I use Thrive hermit crab soaking salt (1 tsp per cup of distilled water).

5. What kinds of food do you feed and how often is it replaced?
I feed 1/2 tsp of freeze dried mealworms, 1/2 tsp of Theive hermit crab food medley, a sprinkle of reptile calcium powder with vitamin D, a few pieces of romaine lettuce and a tiny bit of cucumber. The food is replaced every 3 or 4 days.

6. How long have you had the crab and what species is it, if known?
I have had both crabs since April 12, 2022. Both crabs are Caribbean hermit crabs.

7. Has your crab molted, and how long ago did it happen?
The problem crab is currently molting. The other crab finished a 2 week long partial molt 3 days ago.

8. What type of housing are the crabs kept in, what size is it and what kind of lid is on the housing?
They are kept in a 15 gallon terrarium with a netting lid.

9. How many crabs are in the tank and about how large are they?
There are two crabs. One is golf ball size and the problem crab is about half the size of a golf ball. There used to be a third crab that was a bit bigger than a golf ball, but she died on May 18, 2022

10. How many extra shells are usually kept in the tank, if any?
There are 4 extra shells for the larger crab and 2 extra shells for the problem crab.

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

12. How often do you clean the tank and how?
I clean the waste out of the water daily. And sift through the moss and sand for waste every 9 days. The whole tank gets a thorough wipe down with dawn dish soap and then rinsed every 2 months.

13. Are sponges used in the water dish? If so, how are they cleaned?
There is a sponge in the saltwater dish. It gets cleaned once a month in boiling water.

14. Has anything new been added to your crabitat recently?
Everything in the crabitat has been there since I’ve got these crabs, but the arrangement has been changed a few times.

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.)?
I play with my larger crab everyday. I use to play with the problem crab everyday before he started molting. There is a fogger with distilled water that keeps the tank at an appropriate humidity.

16. Please describe the emergency situation in detail.
My problem crab started molting on April 25, 2022 and is still molting now. There has been no exoskeleton shed. When I pick up his shell, he stays firmly in the shell. He doesn’t smell. The bigger crab did try the bury him at the beginning of his molt but has left him alone since then.

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[aussieJJDude]

Some things regarding your current tank set-up may need some revision to give them the best chance of survival. If you haven't already, the care guides (in the FAQ) is a great resource!

1. Best thing is to replace the substrate. The soil may be fine, if its coconut fibre or 'eco earth', but calcium sand does not make an ideal substrate. In moisture, calcium sand will harden almost concrete like, making it hard to dig. There's concern it could trap crabs in their shells, as they carry water in their shell and over time, the sand could build up.
Ideally, you want the substrate to be deep and an appropriate digging medium. Roughly 3x the height of your largest crab - which usually equates to 6 inches except for larger crabs, made from playsand, eco-earth (coconut fibre) or a combination of the two.

2. The humidity is a little bit of a concern, being that low at night. You mention later you have a screen lid, ideally you want some type of solid lid to trap moisture (and heat). Plexiglass, glass, clingwrap or similar can be used on top of the screen which should help minimise fluctuations in humidity. The temperature is fine however, but a solid lid may minimise variation.

3. If the heat pad can be used (aka not a sticky pad), position it so its on the side, above the substrate line. You want to heat the air rather than the substrate. Depending on location, you may need a large pad, roughly covering the entire back above the substrate line to keep temperature appropriate... particularly during winter!

4. Boiling sadly doesnt equate to distillation, while it will offgas chlorine; heavy metals will still remain. A good dechlorinator will negate the need to boil, as it will detoxify/remove chlorine, chloramine (a growing concern in many areas) and heavy metals. Good example is seachem prime, but other brands are and can be used.
As for the salt, sadly these salts are glorified table salts sold in upscale packaging. Ideally you want to offer salt thats made for marine/reef aquariums, as it will contain trace elements which the crabs will utilise. A common brand as its relatively inexpensive compared to many others on the market is instant ocean, but of course, other marine grade salt can be used. Just avoid aquarium salts, as its is also fancy table salt... you want aquarium salt *for* marine aquariums.

5. I would suggest checking out the good guide. A good variety of foods will ensure all nutritional needs are being met. Biggest issue is the lack of variety, which can lead to malnutrition. Keep it varied and it will ensure all food groups are met, which the crabs can eat a lot of the same foods you can eat! So dinner scraps can be a great alternative.

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12. Many don't clean that regularly, particularly if set up right other than a small spot clean here and there. Regular cleaning can distrust buried moulters, so best avoided unless emergency.

13. Sponges in water dishes can harbour unwanted bacteria unless cleaned daily. If its a natural sea sponge, crabs do liketo snack on it, so it can be left in the tank - just out of the bowl. they drink fine without sponges, and if the bowl is deep, as long as they have easy exit points (eg: rock, fake plants, shells, decor ect) no issue regarding drowning. Many crabs like to swim, so deeper pools are preferred!

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15. Playing with the crabs is best avoided until they at least have moulted in captivity. Many keepers have a hands off approach, and would recommend to avoid handling. Providing out of the tank isnt too cold, they can handle short stints however do a lot better if they just a viewing pet rather than a touch pet.

16. Seperating the two crabs is best, as moulters are vulnerable until harded. A cut bottle top can be used as a makeshift ISO.

[Rae_K]

So if I fix all the problems in my tank, my crab will finish moulting?

[aussieJJDude]

So if I fix all the problems in my tank, my crab will finish moulting?

Its hard to say. Part of the issues why your crab may be surface moulting is that they're current houses in inadequate conditions that dont allow them to do the activities they'll do in ideal setups. It's likely the crab will finish off the moult regardless, but for long term care, its best to rectify some of the tank conditions.