SEARCH THE BOAT GALLEY 
Why Gnatrol
Gnatrol is the best thing we’ve discovered for eliminating bugs (specifically fungus gnats) in our composting toilet. Let’s face it, composting toilets are absolutely wonderful . . . until you get a fly infestation. So the trick is to not get one.
Gnatrol is an organic pest control that specifically targets fungus gnat larvae. And when
NOTE: Sevin dust or liquid will also kill fungus gnats as will malathion. However, both of those are much more toxic, require special handling and should not be used indoors or near water. Gnatrol is a much better alternative.
How To Use Gnatrol
We use 1 TABLESPOON of the Gnatrol powder in about 1-1/2 gallons of coconut coir when we change the compost. I sprinkle it dry over the top of the coconut coir, despite what the instructions say about mixing with water. Then as we crank the compost, it gets mixed in and picks up moisture.
Where to Buy Gnatrol
Amazon used to sell small containers of Gnatrol but that stopped about six months ago. After getting a fungus gnat infestation just the second month of using a substitute, I was determined to find a new source (I really don’t need 16 pounds of it for $455, which is what Amazon offers). You can buy Gnatrol in small quantities in two places that I know of:
Ebay — 1 ounce to 1 pound containers- OrganicBTI (the largest distributor) — 1/2 ounce to 5 pounds
OrganicBTI offers 5% off to readers of The Boat Galley with coupon code theboatgalley (no expiration date)
A 2-ounce container lasted us about 10 months, changing compost roughly every three weeks.
Both offer free shipping in the US; OrganicBYI offers very inexpensive international shipping ($4 for a 2-ounce container).
This article was originally published in March 2019 and updated in February 2020 to make clearer and add the OrganicBTI discount.
Some links above (including all Amazon links) are affiliate links, meaning that I earn from qualifying purchases. Learn more.
Margaret says
Thanks so much for your always helpful info, Carolyn. You’ve helped me from packing our monohull fridge better to our composting head (which we usually love). Just an FYI that in buying Gnatrol from Organic BTI, the Boat Galley promo code got me 5% off, not the 25% mentioned. No complaints here. The company provides free shipping!
Carolyn Shearlock says
Thanks for letting me know that — they may have changed it and forgotten to tell me. I’ll change it.
Tami says
Hi Carolyn, hope Dave’s recovering nicely.
Wanted to share this article, which has just taught me that Bt strain (variety) is very important for critter control. That is likely the reason the liquid Bt didn’t work for you. IIRC, Gnatrol is Bt israelensis (sp), and the liquid at Lowe’s etc is another strain.
Learned something new…
https://gardenerspath.com/how-to/organic/bacillus-thuringiensis/#How-to-Kill-Mosquitoes-and-Flies-With-Bt
Apryl says
I used to get Gnatrol right from their website “gnatrol.com ” and it says website unavailable. Just curious if they went out of business.
So before reading this, I purchased some stuff called Fungus Gnat from Amazon. I followed directions and just applied. However, there are these big blobs that do not disintegrate in the water. I even tried whisking them. So I am not sure if it will work.
I live in Minnesota, so I start all my seeds indoors in January. It never fails…i get those damn gnats. I even froze my garden soil mixture I have made up over the years, and they still appeared. Gnatrol was the only product I have used, and it was very effective. We will see if this “blob” stuff is effective. Otherwise, I will use what you suggested.
Carolyn Shearlock says
The links in the article still work.
Danny says
Thank you for the article, Carolyn.
I’m a gardener and grow fruit tree seedlings inside during the winter. Fungus gnats are the worst! I’ve tried every method under the sun to battle the little buggers and nothing has worked. Thank goodness for Gnatrol! The product is easy to use and works like a charm. We never thought of using Gnatrol in the composting toilet, though. Since reading your article we’ve suggest the idea to our boating friends. We get our Gnatrol in small quantities from figBid.com.
https://www.figbid.com/Browse?FullTextQuery=Gnatrol