It has been a week since I treated the tank with a heavy dose of hydrogen peroxide (H2O2). The reason why I treated the tank was because of hair algae. It was the kind that felt slimy when pulled from the tank. The two flag fish I bought were able to take care of the hair algae on a small scale in a 10 gallon but there were not enough of them to curb its growth in my 40.
I did not measure when I added the H202 but it was about half of a bottle which would mean 8oz or 240ml.
240ml/40gal = 6ml/gal
I have seen recommended dose rates as low as 2ml/gal and as high as 6ml/gal. I believe I went on the higher range.
I did a 5gal/12% water change after 3 or 4 days.
I am happy to report that the H2O2 has killed all of the hair algae and disolved most of it. The few remaining strands that are visible are a greyish clear and clearly dead. There was also some green fuzz algae on the glass that seems to have been killed/dissolved at 90% or better. It has however affected a few species of plants. Most seem to unaffected.
The following seem to be unaffected:
Taiwan Moss - color seems not be slightly duller
Damaged or obliterated by H2O2
Hemianthus Micranthemoides (HM) - severely damaged and browned with some green tips
Stargrass - nearly 100% of every plant is grey/brown and wilted
No affect on GBR, Black Molly, Flagfish
1 of 12 Ottos died as a result, a few others seemed to be stressed but have since recovered.
Full tank view, water appears to be slightly cloudy. Maybe because of all of the dead/dissolved algae/plant material
Right side. Shows the decimated star grass
Close up of the baby tears (HM). They weren't the greatest before but had no chance with the hair algae covering them. I couldn't remove it physically from the delicate stems.
In my experience H2O2 can and will kill anything in the right amounts. I once soaked an anubias (thickest leave/stem plant I can think of) for 15 minutes in H2O2 and it chemically burned it to death. Thinner more delicate plants like foreground plants and stargrass are more susceptible.
Algae in nearly every form I have seen is the most susceptible to H2O2. That is why I feel like it is a practical and effective treatment
Hope this info helps to draw your own conclusions.