now its only 15l will be bigger after looking for a per liter or gal max
You should never add a concentrated hydrogen peroxide solution directly to your reservoir. Always reduce the concentration first by mixing one part of the 35% concentrate with eleven parts of water.
So if you take one ounce of food grade peroxide, mix it with eleven ounces of water to get a 3% solution. Always use fresh distilled water if possible for best results.
The recommended amount of 3% solution of peroxide per gallon of water in hydroponics is around 3ml per liter or 2-3 teaspoons per gallon of reservoir water. Please note that we are talking about the diluted solution, NOT the 35% concentrated peroxide.