Hydrogen peroxide is a reactive oxygen compound that kills microbes by oxidation, then decomposes into water and oxygen. In growing it is used to sanitise reservoirs, tubing, trays and tools between runs, and sometimes dosed into a reservoir to suppress pathogens in a sterile-style system.
In practice
Retail peroxide is commonly 3%; stronger 12-35% grades are corrosive and need gloves and eye protection. In a running reservoir, peroxide breaks down within hours to a day or so, faster in warm, organic-rich solution, so it gives no lasting protection unless re-dosed. It does not distinguish good from bad microbes: it will wipe out a beneficial programme, and high doses damage root tips. Dosing guidance varies widelybeing reviewed.
The oxygen it releases is brief and small; it is not a substitute for aeration and cool water.
Don't confuse with
- Dissolved oxygen: oxygen gas held in solution; peroxide is a separate oxidiser.
- Hypochlorous acid / chlorine: other oxidising sanitisers with longer-lasting residuals.
Myth check
"Peroxide oxygenates roots" overstates it; oxygen release is brief. Using it to rescue root rot can help clean the system but does not fix warm, stagnant conditions that caused it.
