HCA: Hermit Crab Association

This morning when we went to change out their "snack" (some egg, all three crabs had gone under to molt so we didn't think they were going to come up for food but we wanted them to have something just in case) there was a gnat on one of their food bowls. We're thinking it came to the stinky egg which had rotted, but we also have three molting crabs and (unfortunately) a deceased crab in the tank, which had been there for around 4 days because we were thinking he was still alive. I read gnats don't harm hermit crabs, so I'm assuming they don't harm them when they're molting either, but we're scared they came in underneath the lid and don't know if any harmful bugs will get in as well.

We only had one mite infestation a couple months ago (it looked like there were HUNDREDS of them!!!) but got rid of them by half-way bathing the crabs (they weren't cooperating with us) throwing out all the dirt, boiling all the shells twice, getting rid of the piece of wood they had, and finally switching to a whole other tank because we had bought them a bigger one and needed to do that anyway. Needless to say it got rid of them but with three molting crabs we can't really do that again.

We saw another hermit crab owner on this forum wrapped their tank's lid area in saran wrap to keep out ants (can't find the thread anymore) and thought we could do that, but some of us are worried that the crabs would use up all the air in their tank before it was time to refill their water bowls. (Also, could the heat lamp MELT the saran wrap to the tank???) We also thought about buying those sticky fly traps and putting them around the lid, but are afraid the humidity when we opened the tank would ruin them /or/ the traps wouldn't work at all and they'd just crawl/fly right past them.

So in short: We don't know what to do. Are there any ideas that would be guaranteed to keep all bugs out, without harming the crabs inside? They also sit next to a window, which we blocked out with many curtains to keep heat from getting in, but maybe some bugs can get past. We've also had some spiders coming in (North America Jumping Spiders, I think) and are not sure if they'd be able to actually PUSH OPEN the lid to get in. Help?

EDIT: What if we put packing tape (you know, that big clear tape you use to tape boxes shut?) around the lid? We did that in areas when we first added in plants, because we were afraid they'd figure out a way to get to the lid and escape. Would using tape be any different from saran wrap though?

Hi! So were the mites ON your crabs?

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I think regular food mites aside from the ick factor, are pretty much harmless. I believe they look like itsy bitsy lil sesame seeds crawling on the food.. which will happen if you feed fresh consistantly. From what ive read, i could be mistaken. This community suggests isopods for the tank, lil insects that eat all the left overs and feces and things and clean up around the tank... theyre also icky lol. I wiped em out by feeding dry foods ive oven baked or bought online, and feed fresh only so many times a week and i only leave it in a short time. Hope this helps. Im sure other more experienced crabbers will jump in here lol

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you could potentially tap on cheesecloth onto the top and keep most of the smaller critters out. Other than that, i cant think of anything else, but with all the creative people, im sure they will suggest something.

I don't think you'll be able to totally bug proof your tank as things like gnats lay their eggs everywhere warm and moist so they'll always pop up. Some people have had luck setting up vinegar traps on the OUTSIDE of the tank. Others have tapped something sticky to the outside of their tank to trap ants and such from getting inside the tank.

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You can make a vinegar trap and place it inside the tank. Use a water bottle and mix apple cider vinegar, honey or dissolved sugar, and a drop of dish soap. The mixture should smell sweet, but make sure the crabs can't get to the inside of the bottle or knock it over. Another good method is to take a thing of fly tape and stick it near the lid where the crabs can't get to it.

Hi all!

No, from what I could see the mites weren't on the crabs themselves, but we wanted to make sure we got rid of any eggs/larvae that might've gotten stuck to them. We've bought some cheesecloth and we're going to put it up in the morning. We haven't seen anymore gnats near/around the tank (we've seen some food mites, but we're given up on getting rid of those) but today when I was rearranging their tank I found some old food underneath one of their huts. It looked like eggshell and freeze-dried jumbo krill, but it must've been in there awhile because the eggshell looked old and the krill had already rehydrated and swelled. I was scooping it out when I noticed a small white worm crawling on it! I immediately scraped up the food and surrounding substrate (it wasn't in a bowl, it was laying on the coco fiber) and tossed it out.

I'm not sure what it was, aside from the obvious -- a maggot. But it looked too small. It could've been a springtail, but I didn't see any legs or antennas. But I didn't look too closely, so I have no idea what it could've been. I only saw the one, but could there be others hidden in the substrate? All three of my crabs are molting, and I only know the exact location of one and the general area of the other two, or I would do a deep clean. Should I risk digging them up in order to replace the substrate?

EDIT: Also, some of their cholla wood had some fuzz growing on the inside of it. I don't know how long it'd been there, but I tossed out all of it. The wood was on the other side of the tank from the 'worm' so I don't think they're connected.

Sounds like a maggot to me. I wouldn't worry about a deep clean.

As far as cholla- mold is not harmful to the crabs- I wouldn't toss it. Most mold dies off eventually. You could always do a dechlorinated marine saltwater soak of the cholla to prevent future mold growth! Good luck!


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Hi around my hermit crab tank I put some baby powder to prevent ants getting in the tanks. Ants won't cross over baby powder.

I've been fighting (and losing) the battle against fruit flies/gnats! I put traps around the tanks and change out the foods. They don't hurt the crabs, but they annoy me to no end!

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Has anyone tried carnivorous plants to combat pests? I’ve been thinking about getting a butterwort and placing it somewhere the crabs can’t reach it, but where the gnats will. Thoughts?

lovemycrabbies wrote:Has anyone tried carnivorous plants to combat pests? I’ve been thinking about getting a butterwort and placing it somewhere the crabs can’t reach it, but where the gnats will. Thoughts?

I’m not sure this will work in the long run. Most pests are breeding in the tank and will be attracted to the food, heat, and moisture. If the plant isn’t right on top of them, i.e. right next to the food dish, most of the insects simply won’t bother with it since they have more attractive targets.

Even so, there are only so many insects a single plant, or even several, can catch and ingest. It is possible for a plant to have too many nutrients.

It’s a neat idea, but not efficient enough to be practical.


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For the gnats, are they getting out of the tank? If so, you can take a regular water bottle, cut 1/3 of the top off. Then invert that inside of itself so it looks like a funnel going back into the bottom of the bottle. Fill the bottom of the bottle with apple cider vinegar. The gnats will be attracted to the smell of that, fly into the bottle, and will not be able to fly out if the seal is tight. Good luck!

Edit: this is for outside of the tank. Not for inside

HermitCrabFan wrote: ↑

Sun Aug 13, 2017 12:53 am

Hi all!

No, from what I could see the mites weren't on the crabs themselves, but we wanted to make sure we got rid of any eggs/larvae that might've gotten stuck to them. We've bought some cheesecloth and we're going to put it up in the morning. We haven't seen anymore gnats near/around the tank (we've seen some food mites, but we're given up on getting rid of those) but today when I was rearranging their tank I found some old food underneath one of their huts. It looked like eggshell and freeze-dried jumbo krill, but it must've been in there awhile because the eggshell looked old and the krill had already rehydrated and swelled. I was scooping it out when I noticed a small white worm crawling on it! I immediately scraped up the food and surrounding substrate (it wasn't in a bowl, it was laying on the coco fiber) and tossed it out.

I'm not sure what it was, aside from the obvious -- a maggot. But it looked too small. It could've been a springtail, but I didn't see any legs or antennas. But I didn't look too closely, so I have no idea what it could've been. I only saw the one, but could there be others hidden in the substrate? All three of my crabs are molting, and I only know the exact location of one and the general area of the other two, or I would do a deep clean. Should I risk digging them up in order to replace the substrate?

EDIT: Also, some of their cholla wood had some fuzz growing on the inside of it. I don't know how long it'd been there, but I tossed out all of it. The wood was on the other side of the tank from the 'worm' so I don't think they're connected.

Sounds like a very unsanitary tank you've got there! Gnats/fruit flies are normal at times, but to have mites, mold, and maggots too? That is really disgusting! It doesn't sound like you are properly cleaning out their food everyday! It is no wonder your crabs are dying and the other 3 are hiding. When crabs dig under the sand it's not always because of molting, but because the tank is so dirty and the temperature is bad. In order to get rid of all that mold and keep it clean you must air it out sometimes! You must clean the tank and replace the food and water everyday! There should be no reason why there are maggots and mold growing on the food unless it isn't cleaned out everyday! It just sounds very unsanitary as that is not normal. Fruit flies, OK that us normal. But maggots, mold, mites, and other dead things? How dreadful it must be for your poor hernit crabs! Please clean out their food daily and get some air in there every once in a while. It will actually be good for them. Hermit crabs need humidity, but more than that is a clean tank and clean air!

This thread started 6 years ago and hasn't had a response in 4 years. OP hasn't even been on the forums in 5 years. Please check dates before necroing old convos. I'm locking this due to age.