H2o2 , how much for algae?

How much h2o2 do i put in my water to kill algae? I guess light was leaking in and algae started to develop on the side of the tanks and and on some of the roots so I am going to light proof tomorrow but also want to kill it now. thanks guys.

I would start out with a teaspoon per gallon and see how it goes. Do this about every 3rd day. If you see improvement, continue this dosage. If no
improvement, increase the dosage, but not more than every 3rd day. I use this dosage as a prophylactic every 3 or 4 days to prevent problems right thru harvest, and people tell me I produce sweet bud.

Also make sure that you drain, wipe down, and refill with fresh water and the peroxide..I used 3% and one tablespoon for 3 gallons of water which is a small dose to many but it worked great for me. I never had a problem with algae after I covered everything and made it light proof

BTW, I use 35% H202. I don't believe 3% will cut it.

50% grade H2O2 use 1ml per litre of nutes every 3 or 4 days.
35% grade H202 use 1.7ml per litre of nutes every 3 or 4 days.
17.5 % grade H202 use 3ml per litre of nutes every 3 or 4 days.

But, with you already having a problem with algae, give it a once off double dose. It wont harm the plant.
Also, your nutrients have to inorganic. H2O2 will break down the organic nutes as well.