HCA: Hermit Crab Association

So I ended up getting a 15ish gallon reptile setup with a heat lamp, a heating pad and mesh lid from kijiji. I am wondering how common fungus gnats would be in a hermit crab setup. It seems everytime we bring in plants, always we get them.

Would 4 small hermit crabs be too many?

4 small hermies in a 15 gallon would be fine. I have fruit flies sometimes in my enclosure and the hermies dont seem to mind them

Keep in mind that they will grow quickly in good conditions. A 20 gallon would be better.
As long as you plan on upgrading soon the 15 will do for now.

A 15 can have the same footprint of a 10 gallon or a 20 gallon depending on if it's tall or long. If the crabs are really tiny you should have two or three years before they get too big and run into trouble. Just be generous with the substrate!


Fungus gnats will spread, so if you're getting them in plants they'll probably find their way to the crab tank as well. They'll be harmless, but they are kind of annoying. If you're lucky most will drown in the water dishes!

Thanks for the replies! I would have liked to get a bigger tank, but the cost was too good and thought it would be a good size. Assuming the tank makes it 2-3 years, I don't mind upgrading. So fungus gnats are not a huge problem I am assuming. That is good. Do they reproduce in the substrate?

They do, but the maggots are so tiny they're hard to see. I've heard you can trap them with a raw potato placed upside down on the substrate. Yellow sticky pads work as well, but the crabs would get stuck to those, too!

When I recently got gnats in my crabitat, I put some flypaper out of reach in there. No one got to it. Except all the flies, fortunately.

They were gone in like 3 days.