Hydrogen peroxide for hydroponic systems
How growers dose a reservoir in parts per million and clean an empty system between grows, with a calculator for any reservoir size.
Hydroponic growers measure hydrogen peroxide in parts per million (ppm), the same way pool and hot tub owners do, and most run a reservoir somewhere between 25 and 50 ppm. That works out to very little: a 10 gallon reservoir at 25 ppm takes about half a teaspoon of 35% or two tablespoons of 3%. The calculator below doses any reservoir size, and also mixes a 3% cleaning batch for between grows.
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- Dose charts, 5–100 gal
- Cleaning between grows
- Printable reservoir log
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Reservoir Dose Chart
How much to add for about 25 ppm, starting from a reading of zero.
| Your peroxide | 5 gal | 10 gal | 20 gal | 50 gal |
|---|---|---|---|---|
| 3% | 1 tbsp | 2 tbsp | ¼ cup | ⅝ cup |
| 12% | ¾ tsp | 1½ tsp | 1 tbsp | 2½ tbsp |
| 35% | ¼ tsp | ½ tsp | 1 tsp | 2½ tsp |
Amount to bring a reservoir from 0 to about 25 ppm. For 50 ppm, double it. If your strip already shows some peroxide, add only the difference.
How to Dose Your Reservoir
- Test first. Dip a hydrogen peroxide test strip in the reservoir so you know your starting reading.
- Measure the dose. Use the calculator or chart. If you already have some peroxide in the water, add only enough to make up the difference.
- Add it near the pump. With the pump running, pour the peroxide slowly near the pump intake or air stone so it mixes in quickly.
- Keep it separate from nutrients. Add peroxide on its own, not mixed into nutrient concentrate. Many growers add it a few minutes after nutrients have mixed in.
- Retest in 15 minutes. Test away from where you poured. Peroxide breaks down over a day or two, so most growers test and top up every few days.
Cleaning an Empty System Between Grows
Drain and rinse
Empty the reservoir, pull the plants and media, and rinse everything with plain water to clear out loose debris and nutrient residue.
Scrub with 3%
Wipe or scrub the reservoir, lids, net pots, trays and channels with 3% peroxide. Run some through the pump and tubing.
Rinse well, then refill
Rinse every part thoroughly with plain water before refilling and adding nutrients. Never run 3% through a system with plants in it.
Tips and Cautions
Test, don’t guess
Strips that read 0 to 100 ppm make dosing simple. Test before every dose and keep a simple log.
Warm water uses it faster
Peroxide breaks down faster in warm reservoirs, so expect to top up more often in summer or under hot lights.
One product at a time
Don’t pour peroxide into nutrient concentrate or mix it with other additives in a cup. Add each to the reservoir separately.
Handle concentrate carefully
Wear goggles and gloves when you measure 12% or 35%. A small measuring spoon you keep just for peroxide makes tiny doses easy.
Store it safely
Keep concentrate capped, cool and dark, away from nutrients and other chemicals, and out of reach of children and pets.
If it splashes
Eyes: rinse with clean water for at least 15 minutes and get medical help. Skin: rinse thoroughly. Follow the SDS first-aid section.
Frequently Asked Questions
How much hydrogen peroxide per gallon in hydroponics?
For about 25 ppm, roughly ⅔ teaspoon (3 mL) of 3% per gallon of reservoir water, or a quarter of that for 12%. With 35%, it’s about ¼ teaspoon per 5 gallons.
What ppm should I run?
Most growers keep a reservoir with plants in it between 25 and 50 ppm. Start at the low end and test regularly.
How often should I add it?
Peroxide breaks down within a day or two in a reservoir, faster in warm water. Most growers test every few days and top up to their target.
Can I add it with my nutrients?
Add it to the reservoir separately, not mixed into nutrient concentrate. Many growers mix nutrients first, then add peroxide a few minutes later.
Why are my test strips reading zero right after I added it?
The peroxide may not have mixed through yet, or the strip was dipped where you poured. Give it 15 minutes with the pump running and test from another spot.
Should I use distilled water to dilute it?
For reservoir doses you add the peroxide straight to the reservoir, so no pre-mixing is needed. For a 3% cleaning batch from 12% or 35%, use distilled or DI water.
Need a different strength? Our dilution calculator works out any mix from 3%, 6%, 12% or 35%.
Free PDF guide
Take the hydroponics guide with you
- Dose charts, 5–100 gal
- Cleaning between grows
- Printable reservoir log
5 pages · by email (and text, if you like)
Check your inbox
We sent a download link to . It can take a minute to arrive. Don't see the email? Check your spam or promotions folder.
Disclaimer
Information only, used at your own risk. This page and calculator share general information about how hydroponic growers dose and use hydrogen peroxide. Results are estimates based on what you enter and on a starting reading of zero. Systems and plants vary, so start low, test often and watch your plants. You are responsible for how you mix and use hydrogen peroxide.
No product claims. Hydrogen peroxide sold by Bulk Peroxide is not sold or labeled for agricultural or hydroponic use, and nothing on this page is a claim about what it does for plants, roots or water. Check compatibility with your system’s manufacturer and always follow the product label.
Handling. Concentrated hydrogen peroxide can cause serious burns to skin and eyes and can damage clothing and surfaces. Follow the product label and Safety Data Sheet, wear protective equipment, and keep it away from children and pets.
Limitation of liability. To the fullest extent permitted by law, Bulk Peroxide disclaims all warranties regarding this information and is not liable for any damages, including loss of plants or crops or damage to equipment, arising from its use.