Pondering peroxide

When and how much hydrogen peroxide should I use in my hydroponic solution?

Hydrogen peroxide is a powerful oxidizer that can be used to destroy fungi, molds, bacteria and other infectious agents as well as some pollutants. Adding it to your water helps plants by destroying infectious agents and by adding oxygen to the roots’ environment.

Hydrogen peroxide is an essential ingredient in maintaining a clean growing room. It replaces chlorine bleach, which is antiseptic but harmful to breathe. When added to reservoirs, hydrogen peroxide slows the growth of algae and other water organisms so that trays and utensils need to be cleaned less frequently. Soil and water borne diseases such as pythium and other stem and root rots occur at much lower rates in hydrogen peroxide-enriched water. Hydrogen peroxide works because of the oxidative reaction, so micro-organisms are unlikely to develop a tolerance.

There are many ways to add hydrogen peroxide to the water. A measured amount every three days is the crudest method, but still effectively enriches the water. A smaller measured amount daily would even out the peaks and valleys of oxygen in the water. Another method is to use a drip similar to an IV bag, which continuously adds a regulated amount. The most sophisticated method is a probe which measures the oxygen content of the water as an indirect means of measuring the hydrogen peroxide, and adds an appropriate amount as needed.

When used properly, hydrogen peroxide can keep infections in the garden to a minimum and stimulate root growth by increasing the oxygen content of the water. Hydrogen peroxide degrades into free oxygen and water over a three-day period. Some of the oxygen dissolves in the reservoir water and is used by the roots.

Different concentrations of hydrogen peroxide solution are available. It is sold diluted to 3% in drug stores. Some indoor garden shops sell 10% grade and 35% grade is sold in a few health food stores and over the Internet. The 3% hydrogen peroxide solution can be used topically to sterilize cuts and infections. Hydrogen peroxide solution at 10% burns skin. 35% hydrogen peroxide solution acts much like a concentrated acid and is handled as a hazardous, corrosive liquid.

The 10% hydrogen peroxide solution is sometimes used at rates as low as one ounce per 10 gallons water; however, enrichment using an ounce per gallon is more effective for disease control. When 35% hydrogen peroxide solution is used, it can be added at the rate of three ounces per 10 gallons of water. If a 3% solution is used, use three ounces per gallon of water.

ZeroTol is a peroxide-based commercial sterilizing agent used in the greenhouse industry. Its active ingredient, HO2, also breaks down into oxygen and water, but it is even more active than 35% hydrogen peroxide. It is used at the rate of one part per 300, or three ounces per 10 gallons, for excellent prevention of diseases and infections. ZeroTol is available from Bio-Safe Systems in Connecticut (1-888-273-3088; www.biosafesystems.com) and through some other gardening supply stores.

Readers with grow questions (or answers) should send them to Ed at: Ask Ed, PMB 147, 530 Divisadero St., San Francisco, California 94117, USA
You can also email Ed at AskEd@cannabisculture.com, and send queries via his website at www.ask-ed.net.
All featured questions will be rewarded with a copy of Ed’s book, Marijuana Question? Ask Ed. Sorry, Ed cannot send personal replies to your questions.