I just found out about this as a way to spot treat algae.

I want to know if you guys use this method and how often and has it ever caused any harm to fish or plants?

I would be using it very lightly as I don't have much algae but have a bit.

Hi philipraposo,

I have used Hydrogen Peroxide (H2O2) 3% solution to rid my tanks of BBA (black brush algae) and BGA (blue green algae / Cyanobacteria). If an outbreak occurs I manually remove as much as possible and spot treat areas individually, starting with the worst area first. I dose no more than 1.5 ml H2O2 per gallon per treatment, and only one treatment per 24 hours. I have not found it to be effective for GDA (green dust algae) or GSA (green spot algae). Currently all of my tanks are BBA and BGA free.

For more detailed instructions check out post #4 in this thread.

https://www.plantedtank.net/forums/sh...d.php?t=203684

Good active thread here above

Each thread maker has their own take on the minor details or even whats minor... In the end the stuff shows to be pretty forgiving across usage techniques

I always like to say nobody can accurately tell you whether peroxide is better or worse than any comparative algae management tool, only that if you choose to use it a lot of good info is out there. For the reef tank version of the above search google for pest algae challenge thread its 3x as many tanks.


You are asking if 3% works and nearly all responses will be centered around that percentage

as mentioned since dust and spot algae weren't responding, I went ahead and upgraded to 35% food grade which is highly dangerous. Let's just say they respond.

Video of 35% use is on my youtube channel under "35% peroxide in the pico reef"

I use it quite often in all my tanks. When I don't have livestock in a tank, I use the it liberally. With fish and inverts, I also use quite a bit although not as much. 50ml in a 20 gallon with some circulation. I have yet to see any negatives from using peroxide. My shrimp actually swarm the areas the H202 is working since the are able to eat BBA once it has been treated.

I've only used 3%

i use it all the time. im dealing with a BGA problem. first i remove as much as i can and then i spray h202 on the left over spots of BGA. doesnt come back for a while. its a 20g and i only use 10ml.

I followed the "one-two punch" method as brandon429 mentioned. I had green hair algae growing in a 10 gal. My tank is populated with few types neos, crs, cpd, and micro rasboras. To be safe I took them all out except for the babies that i couldnt catch or see. followed directions and algae was gone in few days. everything survived, even the shrimp juvies.

Thanks everyone, I think I will try this out soon.

Ive used it and it definitely works but too much of it will kill fish/plants

I have used it in several ways against different types of algae.

Remove driftwood or rock from tank and pour on the H2O2 straight (3%). Let it sit until I am ready to put it back, then a quick rinse in a bucket of water. The remnants on the branch are no big deal. Very good results on BBA.

Drain the tank for a water change, whatever will expose the algae and squirt some H2O2 into the densest mass of the algae. Dose 1ml/gal. Reasonable results on BBA, though a second treatment sometimes helps.

One-Two punch @ 4ml/gal with NO LIVESTOCK. Spotty results. I think the water circulation portion of the instructions is very important. Best results in tanks with best water movement.

Add H2O2 to an aquarium where the fish are gasping for air, helps. Obviously I followed it up with a big water change to remove whatever conditions were causing the low oxygen in the tank, so the H2O2 is only the first step in the treatment. But it gave me long enough to get the new water prepared.

use it all the time for hair algae. with livestock 2 ml/gal max and i watch their reaction, good circulation is better IME. just dont use if you have fox tail or riccia, it melts it pretty good. i actually use it with excel at 1ml/gal for 1-2 punch on tough bba or fillament type algae. that combo will burn some mosses as well so be careful. cycling my 120g now and with no livestock (ada is doing it ammonia thing) the algae is going nuts even with tons of stem plants. I just dose 4ml/gal and it kills it all dead. of course it comes back since the tank is no where near balanced or cycled but its easier than trying to manually remove it. I use anti-biotics usually on BGA but at 120g its too much $$. h2o2 is what 99 cents a bottle at walmart.

It will burn BBA but will also burn HC. Harmless to Anubias, Fissiden Fontanus, Crypts, Amanos, Beta.

i alway use peroxide for my alge problem and alway treat new plant from the river with it have never had a problem with it hurting my plants but some be differen i thinc

cool, I wish I had know about this a while ago. Ideally one would want to deal with algae issues by trying to balance out deficiencies first before using algaecide to kill it off. I have gained a lot more control over my small algae.

I had some of my vall melt after using h2o2 but it has come back since. I used about half what's recommended for my sized tank so it could just be that my tank is sensitive. I will say that you can use it as an effective treatment, but you MUST ensure that you find out what caused it in the first place. Try to focus on maximising growth in your plants and you will likely deal with your algae problem as well

How do you spot treat for planted tanks? I dip my coral frags HP works well for reefs with Hair Algae. Im curious