How much H2O2 hydrogen peroxide for Gnats

Hi growers. I bought H2o2 (hydrogen peroxide) to control gnats in my grow space… I wanted to know the ratio I should use… Because I have 50% hydrogen peroxide which is extremely concentrated and I can’t afford any damage to my ladies as they are in flower already

Welcome to our world of growing here at ILGM and to our awesome comunity.
Here is what you need. Please feel free to ask ok.
.LM.kkiix one part 3% hydrogen peroxide with four parts water. … Contact with hydrogen peroxide will kill fungus gnat larvae on contact. After a few minutes the fizzing stops an,d the peroxide breaks down into harmless oxygen and water molecules.iik

Yeah I know that but I have 50% hydrogen peroxide instead of 3%so how would I mix that?

Tphe peroxide won’t hurt anything.
I would go with 1/8 th per perox ide to a gal of water and see how that works for ya. If need be just add more peroxide. I have found that when killing bugs stronger is better.

So my plants won’t be affected at all by this?

50% Peroxide Dilution

To make your own 3% and 6% Hydrogen Peroxide solutions from 50% solution, for use in the Sochting Oxydators, follow the instructions below:
Caution should be used when dealing with 50% Hydrogen Peroxide – it can burn the skin. Use gloves and protective eyewear as a precaution.
6ml of 50% Hydrogen Peroxide in approx 94ml distilled water = approx 100ml of 3% Hydrogen Peroxide
12ml of 50% Hydrogen Peroxide in approx 88ml distilled water = approx 100ml of 6% Hydrogen Peroxide
for larger volumes of 6%:
120ml of 50% Hydrogen Peroxide in approx 880ml distilled water = approx 1000ml of 6% Hydrogen Peroxide

Ideally – store the liquid in a used Hydrogen Peroxide bottle, or in a bottle with a pressure relief lid – this is because the Peroxide will increase in pressure over time particularly with higher temperatures…. keep it away from light too….

The above was copied from another webpage…
Once you have a 3% solution you can then dilute further for your needs. Like the 4 to 1 mentioned earlier



Thank you for that copied to my many files But mostly for helping him with the gants.

B Safe

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No problem…
My buddy has a 55 gal drum of 35% peroxide for his business and it will burn the skin right off your hands. While its completely safe at low dilutions it can be very corrosive at high concentrations.

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How much would you use in ml per gallon for 3%? I don’t know what it means by 1 part to 4 parts, I’m slow.

Using a 3% peroxide mix 4 cups water to one cup 3% peroxide.
The ratio works if you use any unit…quarts, cups, peanut butter jars…Just do 4 to 1.

So if I need to make 4-5 gallons I’d have to use 1 gallon of Peroxide?

One quart per gallon…
So yes,one gallon to four gallons makes 5 total.
Personally I use this stuff.

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Throw a teaspoon full in a bucket of water and wait a few hours then water with it.
The bacteria kills the fungus gnats.


Dont risk us8ng h2o2. Use BTi. Its available on ebay in a pure form, $20 for 2oz, which is enough for a large infestation of 4+ plants. Or as mentioned mosquito bits also contains a diluted form of it.

Only use BTi, other BT strains are not effective.

This is safe for organic grows, living soil, etc. It will not kill off your bacterial biome like h2o2 will.

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Ok thanks I was trying to avoid going to the store it’s kind of a drive. I have BT but I heard it doesn’t kill larvae like BTi does.

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Yea thanks I’ll probably have to go get some.

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You wont regret it. In 2 weeks youll be gnat free. Its the easiest fix.

Ok thanks, I’ve been letting em dry out that’s been keeping the adults away. Also do you agree how much, just teaspoon? I thought I’ve seen someone mention throw like 2 oz in a bucket. I could be wrong.

Right. When I had gnats I tried just about everything . Even some various BT’s, but not the BTi. Nothing fully eradicated them. I think it was @Spiney_norman that recomended the BTi. Thanks again. :+1:


Thats what I do with the bits. I bought them for rain barrel mosquito control. Works great. Just happened to find out it works for fungus gnats.
Of this particular product a spoonfull goes a long way. The bits are ground up corn cob with the bacteria on it.
Others buy plain BTi and use it.