Im using Hydrogen Peroxide mixed into the water to control gnats and other reasons, however i wonder if this will kill the useful bacteria in the soil as well?? Since im using Dr Earth Fertilizer Im unsure if this would be counter productive .?
I searched on the forum and I know I have come across this before I have used a diluted solution for WPM and have had good luck. Found this on the web.
**You can water your plant’s roots with a solution of hydrogen peroxide to remove fungus, mold, and rootworms. You can also mist plants that are affected by spider mites and aphids with a solution made of hydrogen peroxide and water. These treatments are very helpful for overall plant health.**To prepare a root drench or a spray solution for use on aphids and other insects on the leaves of your plants, you will need to dilute the hydrogen peroxide carefully. The usual ratio is one cup of hydrogen peroxide for 32 cups of water if you are going to be working on a large number of plants.
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It is my understanding that peroxide will kill off all bacteria.
In my experience the best defense against those damn gnats is not to overwater, if you use soil. A container large enough that allows about 3-4 days between waterings. This will keep the top of the soil dry enough that they will eventually go away. If you are watering as much as every other day you will get them, and they become very difficult to get rid of without chemicals.
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if it kills all bacteria it must not be good for my grow. ok…
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The only time that I would use peroxide in soil would be to treat for root rot. But on the the other hand if running a hydro there would be a bottle of peroxide close by.
If it’s diluted enough it won’t harm anything it’s simply water with an extra oxygen molecule. It helps with nutrient uptake and soil oxygenation. It’s chemical compound is H2O2, it is very useful for
- Encourages and supports Plant growth by supplying oxygen into the soil. Plants absorb more nutrients and grow faster.
- Eliminates soil fungus spores and molds. In fact it can sterilize soil of all pathogens.
- Kills fungus gnats when used as a soil dressing and deters sap sucking insects when regularly applied as a leaf spray.
Using it in different concentrations is effective it would need to be somewhere around .75-1% peroxide to kill any beneficial Bacteria, you would have to drench the soil with the solution.
1% concentration works for gnats just mist the topsoil with the solution and don’t water your plants with it and your microbes and beneficial fungi will be A-OK!
Get Growin!
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Thanks for the reply, I was really loving the benefits of HP however I think i will just stay clear as long as I’m growing organic, and just stick with mosquito bits. Glad to know I didnt destroy the soil though.
I’d stay clear of peroxide and use Diatomaceous Earth instead. You can premix into the soil, or add as a top dress. It also contains minerals your plants need.
“In general though, diatomaceous earth is composed of 80-90% silica, an abundant element found in everything from the earth’s crust, to rocks and sand, and within the cells of plants and animals. It also contains varying amounts of calcium, iron, sodium, and several other trace minerals.”
DE works well for pests but it kills my worms too 
Sticky traps work pretty well
Your technique for misting the top of the soil with a light peroxide mixture makes sense, and I will try to remember this one. Since the peroxide tends to flash off from the water anyway. If you mist the soil during the dry cycle the peroxide will never penetrate the soil very deep at all.
It occurs to me that the the peroxide mist may work to keep gnat at bay. In the top of an AutoPot using coco and perlite.
Peroxide solution sprayed directly on the soil will immediately dissipate and likely not penetrate below 1/4" or so. Your beneficial microbes ought to be just fine.
Peroxide is the growers’ friend.
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Just spray the surface to kill the bacteria that gnats like. Use it sparingly as it does kill your good bacteria too. Other than that it’s very safe.
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I regularly mix 5ml/gal with my Water to help increase 02 and nutrient uptake. Soil is just as happy as ever, my red worms and mycorrhiza don’t mind it either, plants are happy so it’s not harming the microbes either.
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When growing organically and working on building a living soil I would highly suggest to stay away from peroxide. You can seriously damage anything that may be living in your soil.
Rather than making foreword progress it will cause you to back step quite alittle bit.
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Glad im top feeding today, and my plants seem healthy still.
The peroxide is detrimental to the beneficial microbes. Best defense against gnats is a stable environment 
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Using a properly concentrated solution correctly as a topsoil applicant your not going to kill your soil.
While too much of anything can be harmful to plants.
Peroxide is simply water with an extra oxygen molecule H2O2 and great for garden use. My living soil plants get a very small dose concentrated to around 0.3% 1 part 3% peroxide 10 parts water at every plain watering. And yes it does kill bacterium, ANAEROBIC bacteria, the ones we don’t like, it’s beneficial to AEROBIC bacteria, the ones we like and too much will kill everything.
AGAIN - properly concentrated is KEY here.
Fun Factotum: H2O2 naturally occurs in rainwater at low concentrations as well.
Your air stone adds O2 to H2O… essentially creating very low concentrations of H2O2…
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I would ditch peroxide and use bti product, something like mosquito bits. Add some sticky traps to get the fliers and call it a day.
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It’s just water and extra oxygen. It will last @ 60 minutes in solution being strongest when first added. I use it to kill any algae that might be lurking in my recirculation system. It helps to keep the emitters flowing properly. When I detect the system may need any, I add it to the return pipes, dividing the desired amount between them. Any additional benefits the cannabis receives are added blessings. The amount varies depending upon who’s opinion or the actual reason you use it. For my purposes, you can safely add 9 tbs = 27 tsp = 135 ml = 5.625 ml per gallon of water for 24 gallons. Many users suggest 3 ml per gallon, but I’m a farmer. Best wishes in your grows.