I use 29% H202 on a daily basis. 14ML dailey per 25 res gallons. Works great. I usually mix it with one gallon of water and pour it in just after lights out. I usually wait 5 or 6 hours at least after putting in any nutes. Increases oxygen in res, and keeps it free of root rot at the same time. Done it for the last 2 years. Just don't add it to the res without mixing it with a gal of water first.