Using Fenbendazole to Control Hydra

By Frank Cowherd (extracted from a PVAS forum thread)


The easiest way to get rid of hydra is with fenbendazole. Go to a Tractor Store and buy a $25 bottle of SafeGuard=fenbendazole (sold as medicine for goats). It is a somewhat-thick white liquid that settles, so shake well before use. While at the Tractor Store buy a syringe so you can measure the dose easily. A 3 or 5 mL syringe is about right. No needle needed. Add one drop of the liquid per gallon to rid adult fish of parasites, even internal ones. To get rid of hydra all you need is a half drop per gallon.


I have used this dose on fry tanks without loss of fry but destruction of all hydra. Never use repeat dosages of SafeGuard until after 3 days. Repeats can only be done after 3 days and after a 50% water change. But for hydra there should be no need to do so. I suspect the half drop per gallon is sufficient to remove most parasites from plants. That is, two gallons of water with a drop of SafeGuard could be used as a dip (a couple hours to overnight) to treat plants you bring into your fish room. But it would not like destroy snail eggs. Potassium permanganate (PP) can be used to do lots of things including destroying hydra and parasites and dipping plants. But PP is a solid and will stain most anything it touches.


The concentration is critical to what you are trying to do. I use it each spring to clean up my ponds with out killing the fish. And when it is spent it forms a hazy brownish color to the water. This can be cleared with hydrogen peroxide to give a crystal clear water. Jim's calculations given in his note seem good and obviously work. One teaspoon of the PP dissolved in 100 mL water gives a stock solution. This should be stable as long as it is capped tightly. Adding one drop of this stock solution (assuming the dropper gives 20 drops per mL) to one gallon of water, produces approximately a 1 ppm PP solution. If the dropper only gives 10 drops per mL, then the solution formed in one gallon of water would contain close to 2 ppm PP. When working with either SafeGuard or with PP it is always better to be in error on the low concentration side since high concentrations can cause fish death.

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