peroxide for blue algae


Guru Class Expert
Jan 6, 2006
I had lot of cyano problem in my 50g. I found on internet the idea to use peroxide to kill it. so I add the equivalent of 1 ml of peroxide per 5 to 10 gallon of water. to inject the peroxide, I sused a seringle and injected that peroxide strait on the cyano. I dit that again and again every 5 to 6h.

Result: if treated the day the cyano appear, the peroxide kills it in 24h to 48h. it reapear beacause it do not solve the reason of that problem but it gave me the chance to look for the reason I have that cyano without being invaded by the cyano.

What do you think about that trick? it worked for me but i still wonder if it could have side effect I havent notice.

Tom Barr

Staff member
Jan 23, 2005
Well, so does cleaning your tank and doing a water change.
So does antibiotics.
So does a 3 day blackout with a cleaning and water change.

Good KNO3 dosing , if the tank is other wise clean(Filter, gravel etc) and growing well, should address the problem for most folks.

Tom Barr


Lifetime Members
Lifetime Member
Aug 25, 2006
Peoria, IL USA
Getting your ferts and lighting in balalnce and keeping your tank clean is how to prevent algae, but it does get away from you sometimes.
I know some folks that have been using peroxide for BBA and hair algae. What they having luck with is using 1 ml per gallon per week, and doing what you are doing, squirting it on directly on the algae once a week. Shut off the filter and leave off for about 20 min to prolong contact between algae and peroxide. Then do your water change. The peroxide breaks down to water...and it treats the algae by oxidizing it.