Hydrogen peroxide (H₂O₂)..

Hydrogen peroxide is available everywhere as a 3% solution in distilled water with some stabilizers that may include trace amounts of phosphate and harmless ascorbic acid. It is another caustic oxidizer, slightly stronger than potassium permanganate or even chlorine in oxidation potential. Hydrogen peroxide degrades to a molecule of water, freeing an atom of oxygen and leaving no residue. Hydrogen peroxide is unstable. Light will oxidize it; that's why the plastic bottle it comes in is opaque. You should even be careful not to shake up the H₂O₂ bottle unnecessarily.

Hydrogen peroxide has many uses in industrial wastewater management, and it would be more used in fish farming if the FDA would extend its approved uses. Testing procedures for introducing new uses for drugs in aquaculture for food fish are running about $50 million, and without corporate sponsors, testing hydrogen peroxide is a low priority. Testing has been running since 1994!

It has been proved effective against Saprolegnia attacks of fish and eggs and against bacterial gill disease. The FDA continues to withold final okay for the use of hydrogen peroxide to eliminate ectoparasites, but in Hawaiian tests the marine flagellate Amyloodinium, a close relative of freshwater Oodinium, was cleared from fishes' gills. In those tests, juvenile mo'i were found to tolerate exposure to hydrogen peroxide at 150 ppm for 30 to 60 minutes.

If you're very cautious in using it, H₂O₂ can be used in the aquarium too, even to clear green water. It oxidizes dissolved organics, including phenols, and turns odorous thiols and other sulfur compounds like hydrogen sulfide into harmless sulfates.It will also tend to precipitate dissolved iron you may be nurturing for a plant micronutrient. Hydrogen peroxide should be on hand if you're using potassium permanganate, since it will neutralize KMnO₄ if you have overdosed.

It would even break down some inorganic compounds such as nitrites--— but at concentrations that would seriously burn the gills of fishes.

Better read up first on H₂O₂ and its environmental applications and its chemical properties, at www.h2o2.com/ --—a truly excellent site.

Among many biological pathways, hydrogen peroxide is formed naturally (though in very small amounts) by ultraviolet in sunlightreacting with water.

About ozone and ultraviolet radiation.

Both of these are used by some fishkeepers as general disinfectants. The E.P.A. guidance manual "Alternative disinfectants and oxidants" (search the title's keywords) covers the uses of ozone and UV radiation in water treatment. You might want to see this document.