HCA: Hermit Crab Association

Hi all,
I moved my crabitat when I went to grad school, but we ended up being 100% online this semester so I have been living back at my house almost 5 hours away. My roommate has been taking care of my crabs for me and just told me that the crabitat is infested with fungus gnats. We had a persistent fungus gnat problem in the apartment before I left and I'm KICKING myself for not treating it more aggressively before they found the crabitat. It just never crossed my mind that they might end up infesting my tat, which seems so obvious in retrospect.

What should I do? I am not sure exactly how bad the problem is since I haven't seen the tat myself. My roommate says it's pretty bad. I'm not really worried about the crabs since the sticky says they are harmless, but my roommates want me to do something about them since they cannot remediate the fungus gnat problem in the rest of the house if the crabitat remains a fungus gnat fortress. I believe that applying a neem spray to the substrate regularly should solve the problem. Is neem oil toxic to crabs? I assume it wouldn't be good for them.

I can't deal with this issue right now but I might be able to do something about this over Thanksgiving. If neem oil is not an option, I imagine I will have to clean all of the substrate out of the crabitat and replace it. My tat has an extensive egg-crate scaffolding construction that is covered with burlap. Will the burlap have to be replaced as well? Once the tat is cleaned (and sterilized?) how will I prevent the fungus gnats from getting back in? I think I have to assume they will be present in the apartment at least for a little while after I clean the tat.

I will be grateful for any advice. Although this is not a serious issue for the crabs, it sounds like it is a serious issue for my roommates and therefore for me. The idea of sterilizing my crabitat right now is sort of giving me a panic attack. My graduate program is very demanding and driving 10 hours round trip plus the time it will take to deal with my 60 gallon tat is horrifying to contemplate.

I found some online resources claiming that this bacteria called Bacillus thuringiensis var. Israelensis (BTI) kills fungus gnats. Does anyone have any idea if this might be safe for crabs? If it's a bacteria my guess is that the crabs would probably be fine but this is just a guess.

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I have never used the mosquito dunks stuff, but I have seen others in the community talk about it. It could potentially affect crustaceans, if I remember right it can cause issues with isopods, but it's mostly just plain old untested in crabs. Only a few people have used it. However, I don't think its a bad idea and it would solve your problem quick.

Other options would be drying out the surface of the substrate for a while, using potato traps to collect the larvae out of the tank, using sticky traps around the tank to get the adults.

I had them bad at one point in my critter room, but they sort of just disappeared after a while. I've noticed most outbreaks of insects wax and wane if tanks are kept tidy.

Fungus gnats are pretty specific to soils though. Unless you guys are plant obsessed, they shouldn't be getting everywhere in your place! Are you positive of the ID?

Yeah we have plants everywhere in that apartment. I'm as certain as I can be that they're fungus gnats. I found a scholarly article that looked at the use of the bacteria for controlling a pest insect in land crab burrows that found no effect on the crabs so I think ik gonna go for it.

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Don't forget to treat all the plant's soil, too!

Fungus gnats are the worst, they've been in and out of my plants and invert tanks forever . I just wanted to second the advice already given and recommend you give the oil a try! It would be a lot better than trying to deconstruct and clean an entire crabitat.

On the plant side of things, definitely check the quality of your soil. Soil that is wet for long periods of time can make the gnat problem worse, as well as hurt your plants long term. Ask your roommate to dump any standing water in catching dishes/bottoms of pots and to allow your plants' soil to dry out completely before another watering. It will help tank gnat populations overall, including in your tank! Might be worth it to let your crabitat substrate dry out a bit if you can manage it without hurting your crabs as well, along with some decor/food bowl/water bowl cleaning if your roommate will do that for you. I wish my roommate would crabsit for me too!

(Good luck with the rest of grad school, I'm starting next year and I'm nervous lol)