Zinc Oxyde seems indeed to have some fungicide and algaecide properties and it indeed still seems to go around in the pond world as a white miracle powder against algae and pond cleaning product.. Known products are "Algae Away" - "White Powder" (with some Jap symbols and stating it's miniral clay powder, but it isn't calcium chloride is added that's it) - "Eco Pure" with jap koi symbols seems to be a home brand from a not by name mentioned Dutch Koi Company..
but has an GHS Classification in Category 1: Carcinogenic - Dangerous for the environment (N) Fire Daimond - NFPA704
H/R Phrase - H410 - R50/53 - Very toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment.
Because it is an unsolvable powder it has also cleaning properties and polishes the filter hoses clean. So it stays as a fine grainded residue in the soil, fish eat it and the zinc will accumulate in the organs such as the liver and possibly cause ill effects in long term and a slow painfull dead.
If you find or get offered a white powder as algaecide rub it between your fingers and it feels kinda greasy and smooth like baby powder. And your fingers repel water after that it most likely contains Zinc Oxide.
If you still like to poison your aquatic lifestock with it, you can buy it almost at any regular drugstore for 1/10 of the price. So it can be bought anywhere but it's more common sense that a aquarium or pond shop should not recomend and sell it as algaecide because of the above properties of the product. I guess it's also the reason why there is so little information to be found how it actualy works as a product to kill algea because of the hazard classification.
Now that said
.. I lately tried H202 for the first time against clado and staghorn in my moss and plants, it works pretty good on staghorn don't need more than a small dose the moss can take that. Clado is harder to kill and needs an extra treat but that also did kill some of my moss especialy the liverwort, killed 90% of my Pelia with the extra treat. So if i used the sciccors instead on the pelia i would have saved more than i did with the H202. I also did spray some around during a water change on hardware and some plant leaves they took it well. Only the Potamogeton gayi was almost killed by it.
So i never use it again on moss and rather not advice to use peroxide on moss, it definitively damages it. Maybe more than a pair of sciccors does if you use a pinch to much.
