Oh yeah, you reminded me @Enjoi802, a while back when I was rebuilding the room I only had 1 mother left running and she got the gnat. So I hit her with a peroxide solution. It made the soil fizzle which had me a little worried at first as I was not sure if maybe i dosed it a bit high. 
probably. Of course it completely tanked the biology. The plant was happy. I just gave some light salts for a couple of waters with some biology boosters and back on track. The one dose completely blasted the adult gnats, the juvenile gnats and all the lava. It was genocide. I was impressed how well it worked on its own.
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Ditto on both. I also use dunk donuts top dressed.
For the res, I put the donut in a mesh bag. Otherwise it makes a mess crumbling apart.
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I actually read through this thread and found that many have used the peroxide with good effect. And as others have stated and Iāve seen online the roots 707 formula May Be the culprit, maybe the grow store and how they store it. Maybe just the way things had to be. Either way I have won this round.
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I dealt with them all summer. I finally got rid of them using the mosquito bits. Iāve been putting a layer of the bits into every new container I plant.
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Yāall really gotta try the glutaraldehyde. I havenāt seen a gnat in a long time now. Wet coco is like crack to them. Available off the shelf as Flourish Excel for planted aquariums. My āliquid CO2ā experiment happened to have a neat off-label use.
1mL/gallon of Excel. Seems to both kill them outright and prevent breeding. Also an excellent sanitizer that seems to last longer than bleach. Maybe PAA would have the same effects.
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Really?!? Iāve never heard of it for ācleaningā except to knock back nuisance algae in the tank, while it nourishes the plants. My co workers love those seachem plant products, I never got heavy into planted tanks, I went saltwater reef instead.
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I posted this before, but I ordered a granular form of mosquito dunks/BTI from China. It was only $5 and shipping.
1 tablespoon per 5 gallon.
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Seachem makes very good stuff. As with all the hobbyist level additives, itās of course cheaper to buy a jug of glutaraldehyde and mix yourself at the appropriate concentration, but for an off-the-shelf product itās really great. I used it in my planted aquariums almost religiously even with CO2. Keeps stuff nice and pristine. The argument could be made that itās bad for the bacteria in the filter, but my plants, fish, and inverts were happy, some of which were very sensitive. My 1mL/gallon rate is about 2x what youād use in an aquarium. My experiment used 5x. I do not notice my plants now growing bigger faster or yielding any better, I purely use it as my primary sanitizing additive.
I used to get fungus gnats pretty regularly, never bad, just a few, but I despise bugs in my grow, so Iād spray them with whatever, kill them all, and theyād be back in a month or two. Somethinā about wet coco just beckons them. Since the glutaraldehyde, not a single gnat, anywhere. However, the experiment did not deliver the results I had wanted, a bioavailable liquid CO2 additive for non-aquatic plants. Granted, just a little one with 2 clones, a control and a variable, but I guess I was looking for dramatic āfeed me, Seymourā results.
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Man Iām desperate. Iāll give this a shot. Gnats made the jump from my wifeās garden tent (coco) into my hydro. Infestation got really bad too, and plants have suffered for sure.
Should work in an ebb and flow res just fine, yeah?
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I still swear by my Cape sundews. My favorite is the broad leaf variety, just like my favorite cannabis! Straight fungus gnat slayers.
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Watering with spinosad or the bt in mesquito dunks always seems to work for me. You can get the dunks at alot if different stores but you can also order the bacteria in them in bulk online. It can be hard to find sometimes but itās available.
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If itāll work in an aquarium, and works for my hempy buckets, it should work for active hydro.
Iād probably re-dose every week while you wrangle the problem. Iād like to see what this does to a more significant infestation. Iām having success with 1mL/gallon, but I used double that with no ill effects.
Still havenāt seen a single gnat in months at this point, I now use it in every plant, every watering. Itās cheap. It also discourages (but not totally eliminates) algae growth.
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Started using that BTI I recieved from China about 10 days ago. Gnat population seemed like it was finished. Didnāt see a gnat yesterday morning at allā¦saw one or 2 the day before. But when I opened my door this morning, 4-6 of them came flying right out. Iāve been using nothing but the BTI water for the last 10 days.
Hoping this stuff starts knocking this gnat issue back. I suppose there could have been some in the pupae stage when I started applying and this is their last round of flyers.
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Covering the top layer of all pots with sand works really well.
I also like the simple method of spraying the tops of the soil with hydrogen peroxide water mix for several days in a row.
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Not a fan of the sand method.
Going to keep using the bti nutrient solution, but going to start bottom feeding again and applying DE to the top layer.
Might try the h2o2 diluted with water firstā¦thanks for the tip!!
Ok sweet. I put some on order. Iāll give it a shot. 
Why donāt you like the sand method?
Many years ago when I had gnats really bad after I used the sand + sticky traps I literally had zero after a week.
But yeah the hydrogen peroxide kills the larvae on contact.
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If you get fungus gnats you can just cover your medium with steel wool. The gnats trying to get to your medium will get shredded as will any new ones being born out of the medium. After around 2 weeks should will be gone. It may rust a little but steel wool is a non toxic metal so it wonāt harm your plants and will even add a bit of iron to the medium. I have not personally tried this as I have not had gnats but from what I understand it works.
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I reuse my soilā¦half my medium would be sand after watering and sand settling/washing away deep into the pot. Would have to apply sand constantly.
.
Have never heard this before. I imagine the super fine stuff would be best?
I was thinking of buying a bunch of pantyhose from the dollarstore and wrapping my pots up and tieing off at the trunk of the plantā¦nothing in or out.
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From what I read you use coarse steel wool.
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