# H2O2, Learn from My Mistake



## christinamac (Jan 2, 2016)

H2O2 or hydrogen peroxide is often used to spot-treat algae in or outside the aquarium. I knew that by itself hydrogen peroxide is very caustic. But it is an unstable substance that will dissociate on its own into water and oxygen. This process happens even faster underwater, but not as fast as I thought.

Frustrated with a relatively small amount of hair algae that I can't really manually remove from moss, along with fungus that won't stop growing on my driftwood, I decided to try spot-treating these areas with H2O2 underwater. I was tired, and didn't do my research first. I was under the impression that H2O2 dissasociates pretty quickly underwater.

My Big Mistake

I dosed a total of about 22 mL of 3% hydrogen peroxide in my 1.9 gallon aquarium. I found out after the fact that this is 11 to 22 times the recommended amount that should be used. I did not turn off my filter or remove my bio-media, another mistake. After dosing, I watched oxygen bubbles forming on the areas I treated as expected. My fish and snail seemed fine, so after about 10 minutes I left the room to do other things. 

I decided to browse Youtube videos and watched one or two on using H2O2 in an aquarium. It was one of these videos that made me realize I had dosed way too much H2O2 and that if I didn't act quickly everything in my aquarium would likely die. I came back to my aquarium and saw bubbles everywhere. My Betta looked okay, but visibly agitated and there were a few bubbles on his body. The poor snail looked like he was curling into a little ball. The H2O2 had been in the aquarium for about 30 minutes to an hour at that point. I decided an emergency 100% water change was necessary.

Fixing My Mistake

I put the Betta and snail in a bucket with fresh dechlorinated tap water at the correct temperature. I siphoned out about 80% of the water from the aquarium (the other 20% being trapped in the gravel). I replaced the water in the aquarium with aged and dechlorinated tap water matched to the correct temperature and put my Betta and snail back in their aquarium. I waited about 30 minutes to allow all the water in the aquarium to cycle through the filter about 8 times. I then did an additional 20% water change. Knowing that heat (from the 79-degree F water) and light would encourage the dissociation of H2O2, I left the aquarium light on for an extra three hours that night. 

I re-dosed my liquid fertilizers to help the plants recover. I also added a tiny amount of baking soda, just enough to raise my low KH from 3 degrees to 4 degrees. I did this to help keep the pH more stable and raise it since my aquarium pH is normally a little higher than my tap water (a difference of 0.2 to 0.4)--and I had just replaced 100% of the aquarium water with tap water.

When I went to bed around midnight, almost all of the bubbles in the aquarium were gone. My Betta was acting completley normal, but I was worried my snail might not pull through. I expected to find the snail dead this morning. I prayed that I had not also killed all of my beautiful plants that I have been working so hard on. 

The Day After

My Betta looks healthy as ever, the plants seem unaffected so far, and my little snail is alive! I know the snail will take some time to fully recover, but I am glad that he pulled through. Only time will tell if I did any permanent damage to my plants. Since I likely killed off a significant amount of my beneficial bacteria, I will monitor my water paramters closely in case the nitrogen cycle restarts.

*Lessons learned*: Do my research, and don't try anything I'm not experienced with late at night when I'm tired. Also, water changes are my best friend.


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## Aqua Aurora (Oct 4, 2013)

Glad you cough it in time and were not buying new flora and fauna. Btw the fungus on the driftwood forms because of sugars leeching out of the wood. The fungus eats the sugars. However I don't believe Excel or peroxide will get rid of the fungus (if you remove it, it grows back). Best thing to do is boil the [censor] out of the wood to put a fast forward on the sugar leeching (and tannins).


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## christinamac (Jan 2, 2016)

I boiled the driftwood for about 12 hours over the course of three days before putting it in my aquarium. The driftwood has been in my aquarium for about 3 months and if anything I'm starting to see more fungus, not less. My snail has been eating some of it, and I remove what I can. I know that it will eventually go away on its own--I just got impatient and tired of removing it myself.


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## christinamac (Jan 2, 2016)

Well, I'm pleasantly surprised. My plants look better than ever and it looks like I effectively killed off and removed all of the diatoms I was struggling with. I haven't seen any new growth of the other algaes I had either. My aquarium looks super clean and everyone is alive and well. There is still fungus growing on the driftwood though.

Even though my mistake "worked" I still don't recommend repeating it for eliminating algae in the entire aquarium. I put my fish, snail, and plants at great risk in the process and I feel really bad about it.


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## Davo (Feb 21, 2016)

This is a valuable reminder. I've got some diatoms in my 2.5 gallon tank.

Im going to look into using peroxide but will be cautious of the dose.


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## christinamac (Jan 2, 2016)

I just wanted to give an update for those who are still interested.

The fish, plants, and snail are still doing well. There were a few water wisteria leaves that started to melt so I removed them. There were a few areas of Christmas moss that had been succumbing to hair algae, which is one of the reasons I did the H2O2 treatment. Those bits of Christmas moss looked like they were starting to die off, so I removed them. The anubias and cryptocorynes seem unaffected.

My water parameters are fairly normal except for a small spike in nitrites (0.25 ppm), which I corrected with a partial water change. I anticipated a spike in nitrites since I killed off a signicant portion of my beneficial bacteria.


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## RussellTheShihTzu (Mar 19, 2013)

Hydrogen peroxide doesn't work on diatoms. There is even disagreement on whether they are a true algae.

They will normally go away after the tank is well-cycled. Apparently they happen more often on sand substrate which contains silicates. They disappear when the silicates are depleted.


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## 206Betta (Jan 28, 2016)

It's great to hear that everything is healthy now. Could have been a lot worse and glad you were able to fix it.


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