How much H2O2 do I use in hydroponics to fight a larvea pest in the roots?

@growinggranny I have a reservoir of 260L (68 gallon). Did the math, you recommended around 87ml of 12%. The recommended doses I saw on the internet said to us 3ml per L of 3%. Other were a little higher. So it ended up with everything between 195 and 260ml for 260L (0.75ml/L or 1ml/L). Which is a lot higer then what you say.

You can't really overdo on H2O2 - but I would still be a little cautious with the 12%... if, for example, you have a 4 gallon reservoir, you could probably add 1tsp of the 12% and not worry... and if you don't get results, add another tsp...

@growing granny. I have a 12% solution. I forgot to say that. Sorry

I would use a 3% solution... that will kill off most fungus, larvae, etc... plus H2O2 also has the benefit of adding more oxygen to your reservoir.... don't be scared of it. Good luck!