HCA: Hermit Crab Association

So, we came home from the beach with a few stragglers, and now I'm looking for some advice because they don't seem to be doing well and I don't know if it's just stress or the crabitat is missing something.

These are Northern Gulf Coast hermit crabs, I believe striped hermit crabs. There are 3 - two very tiny and one small. The tiny ones have shell openings of maybe a third of an inch and the small one a half inch. They were very active the first day and during travel. The second day we purchased crabitat equipment and they seemed much more lethargic so I rushed to get them moved to a larger environment with more water/aeration/filtration, but they have not perked up at all. All three are definitely still alive (moving very slightly) but hanging limply about half out of their shells and not really moving - it's been about 12 hours since crabitat completion and they haven't moved in that time.

We transported them in a 1 gallon container filled with their ocean water and their beach sand. Their new tank is a 10 gallon aquarium with filtration, PH is 8.2, salinity is 1.024, temperature is 78. Made the saltwater from our (well) water with water conditioner just in case and API aquarium salt, which is all the local store had though I have some instant ocean arriving today that I can change it out with if need be. I added it slowly to the ocean water they were in, adding a little more every 15-30 minutes until it was half ocean and half homemade. Added more quickly after letting them hang out in that for an hour or so but still took a few hours to add the next 3-4 gallons. I've added 24 lbs of hermit crab subtrate which is plenty for digging but not quite enough to give them a beachy area out of the water.

When I first transferred the crabs there was a beachy area and two of the three crawled up on the sand and hung out there (still not moving, but inside their shells) so I'm not sure if maybe they need more beach? What I found online indicated usually these type of crabs are underwater all the time except occasionally to forage or breed. I can remove some water to expose the beach until I can get more sand, but then the filter probably won't run during that time. I've fed them a variety of shrimp and hermit crab sinking pellets - they ate the shrimp especially very excitedly but haven't eaten at all that I can tell since I moved them into the tank. Any ideas what to do or do we just have to wait and see? Anything that could be hurting them I haven't thought of?

They don’t need a beach. Get rid of the land area entirely, it takes up space and if you have it sloped you risk anaerobic pockets where gases don’t diffuse. If they’re broken the sulfur will spread through the water.

Same goes for the rest of the substrate. You don’t need that much for a saltwater aquarium.

Additionally, hermit crab substrate is designed for terrestrial hermit crabs, not marine. Don’t use it underwater, it’s a calcium product, not sand.

Aquarium salt is trace electrolytes only and is not for marine life, which require a marine salt. Please don’t use it in a saltwater aquarium.

I am most concerned about ammonia. How long did the filter cycle and what are your readings for ammonia, nitrite, and nitrate?


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The filter has been on continuously since about 7 PM last night, so 18 hours, about 5 gallons of water currently in the tank along with the sand it's about 3/4s full, and I can leave it on or do intermittent cycles. I kind of figured I'd keep it going while the crabs seemed lethargic to make sure to maximize aeration and minimize toxin build-up.

So would you go ahead and swap out the aquarium salt water with instant ocean water right away, I was planning too but then with them acting so limp I didn't want to introduce more stress by doing another water change or moving them, but it has arrived so I can make it and do that now if you think it would be beneficial. I don't have a test for ammonia and nitrites so I'm not sure but I am checking to see if the other farther pet store has one this evening.

I got the not-calcium hermit crab sand, it's this product: "Fluker's All Natural Premium Sand Substrate Mixture for Hermit Crabs" and it's also mixed with the sand from their own beach so I think it really is sand, right? Should I remove it? I also put in a few shells for them that we had from the beach (not a huge selection of pristine shells since they are pretty much all occupied unless they have holes though I even added a few of my better quality chipped ones in case they'd be interested) and have more arriving today, nothing painted.

Cycling the filter can take months and should be done before livestock are added. I highly suggest getting a test kit so you can monitor your nitrogen levels. As of now your filter isn’t doing anything useful so ammonia is building up. A large water change would be beneficial to both a) get the right salt in and b) remove the excess ammonia. Since your filter isn’t cycled you’re looking at multiple water changes a week, depending on how quickly the ammonia is accumulating.

See Fishlore’s guide: https://www.fishlore.com/NitrogenCycle.htm

Ammonia and nitrite levels will both be zero when your cycle is complete.

I would still remove the extra substrate, you don’t need it that deep. Marine hermits aren’t regular diggers like terrestrial ones are.


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Okay, will do as soon as possible then! I also read there is a product that helps strip nitrites out of the water, can I add that to help them out do you think? We are going to be out near the big store tonight which I'm sure has this stuff - I didn't count on the local place being out of basically everything when I agreed to this endeavor, thank goodness for overnight shipping.

You can try it, but do your research. Not all products are permanent and none replace water changes.


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Okay, update: one crab has left its shell, still alive but I assume that's not good. Others are still in place but lethargic.

Managed to get test strips and the nitrite remover. Ammonia level upon returning home is 1.0. Immediately changed out as much of the water as we could - probably 50-60% and added the nitrite remover with the water change. Tested 45 minutes later and ammonia level is already down to .25. Plan is to test again in an hour and possibly do another water change later tonight, definitely again in the morning. Also not sure if it's good or bad or irrelevant but the crab who left its shell has moved around the habitat near another shell of similar size to the one he left and is a little more active/responsive to seeing me at the tank wall so I'm probably more optimistic than I should be but I'm guessing the prognosis is not great regardless.

This may help you cycle your tank a little faster. It contains the beneficial bacteria your aquarium needs to break down ammonia and nitrites. It def helped me when I lost my filter and media in a move last year. With this, my ammonia never reached above .05 ppm.

https://smile.amazon.com/Tetra-SafeStar ... 469&sr=8-3

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That crab needs a shell. We have a re-shelling guide but it’s for terrestrial crabs, so if you try to isolate it you’ll need to keep it submerged in saltwater.

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