Tank infested with black gnats

Good friends in a pinch! Forums Chewin’ the Choya Tank infested with black gnats

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This topic contains 6 replies, has 5 voices, and was last updated by  Stacy 10 months, 3 weeks ago.

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    Has anyone dealt with gnat infestations of their tanks?
    My 50-gallon hermit crab tank is INFESTED with black gnats. I use Eco Earth and sand for the substrate. However, I mixed in some hay substrate for fun… but that was a mistake. Also, my tank’s lid is inadequate to keep out flying bugs.

    I noticed the gnats about a year ago and I did substrate changes, but I never fully got rid of them. And this week, the infestation is horrid – worse than I have ever seen.

    So, now, there are thousands (if not millions) of black gnats/fruit flies in my tank. They are flying, in the substrate, and crawling on the hermit crabs.

    How do I get rid of these gnats for good?!


    Maxwell Isenberg

    Clean all the decor, put in new substrate, make a sealed lid that holds the humidity in and doesn’t let gnats in, and bathe the crabs in saltwater to kill all the gnats. When bathing the crabs, bathe them in salt water and submerge the crabs for 10m each. This insures that the gnats will die.



    When you get everything cleaned and back in place, feed only dry type foods for a bit. Wet foods will reattract flies. You can try to make a trap by placing some overripe fruit in a cup and the make a sloppy sort of covering with saran wrap. The point to making is messy is that with lots of folds and bends the gnats will get stuck trying to crawl through it and die.


    Gregory Chrislip

    Better trap, mason jar with saran wrap stretched over the top and held in place by a rubber band. Poke small holes in the film with a toothpick. Flies crawl in and cannot leave. Also works well with apple cider vinegar.


    Anne Grady

    Some people have reported using a vacuum to catch and remove most of the flying mass.



    Update on the black gnat issue:
    I did a complete substrate change.
    I removed all of the shells for a short time. I discovered the gnats were living inside some of the shells. Ugh.
    I gave each hermit crab a bath because the gnats were in their shells as well.
    I put a new lid on the tank.
    I surrounded the outside of the tank with fly tape. (Yes, my room looks ridiculous right now, but effective.) I am letting the fly tape stay up for two months.
    I have 4 gnat traps. Those will remain out.

    Results: Very effective. I reduced the gnat population from 14 BILLION to about 10 gnats. 🙂 They magically reappear in my house from time to time. So, I will keep better watch.



    I bow to Greg’s great bug knowledge lol

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