If we Google something like:https://www.google.com/search?q=hydrogen+peroxide+to+control+algae
We get a lot of pond and aquarium sites explaining how to use hydrogen peroxide to control algae. Some of these sites even explain what hydrogen peroxide is such as…
Hydrogen peroxide is a colorless natural liquid similar to water.
It’s made up of two molecules of hydrogen and two molecules of oxygen, with a chemical symbol of H2O2. [1]
They even give it a footnote to make it look scientific. It would actually be nice if the people that quote things like this had the first inkling of anything to do with chemistry.
This is just the first of several examples of extremely poor information on some of these websites. There are an awful lot of snake oil salesmen on the web selling you products through their links and affiliates.
My first comment about “natural” is that arsenic is also natural, and so is plutonium, and rattlesnake venom. Secondly if you paid attention in high school chemistry hydrogen is not a molecule it’s an atom unless you’re talking about H2. And oxygen is not a molecule it’s an atom, again unless you’re talking about 02. Hydrogen peroxide is not made up of molecules it is itself a molecule made up of atoms. If they can’t figure out that basic chemistry are you really interested in having them tell you how it’s chemically safe for your pond?
Enough about the quote. Here is a reason why you might not want to use hydrogen peroxide in your pond or aquarium. Hydrogen peroxide generates reactive oxygen species. Similar to ozone generators and other systems that generate toxic oxygen radicals. Hydrogen peroxide kills algae by being toxic. My PhD was on how these same chemicals damage DNA and are thus mutagens and carcinogens. So the long-term effect is that you are increasing the mutagenic and carcinogenic processes in anything that lives in, drinks from, or bathes in your water feature. This affect may be relatively small. Algaecides and other commercial toxins are far worse IMO. It also may be more dangerous for a bird to have The neighbors cats in its environment then to drink from your system. There is just no way to do a cost benefit analysis for every living organism that might drink from it. It is probably more important at this level for animals to have water in their environment then that water be entirely non-toxic. That said there might be other ways of approaching that water feature down the road.
Snails and other aquatic life that actually eat the algae instead of kill it might be an answer _if it does not dry out or heat up_ in the afternoon sun. If it does tend to dry up or heat then finding something to shade it might be part of a solution. The permaculture point of view is to not decide you have to kill _everything_ that’s in your way. And bees really don’t care if there’s a little bit of algae and are happy to use it as a landing pad.
There are ways to outcompete the algae. But also, IMO hydrogen peroxide is much much better than algaecide (AKA algaefix). Be well!