In order to answer your question I need to know more about your tank. How many total gallons, what kind of system, reef i assume? Stocking level and other equipment esp if you run an ozoniser. You also need to consider the number of catalysts and the % of peroxide you would be best using not necessarily 35%. Having said that if you can purchase 35% I would probably go for something like at least 10liters depending on the strength of peroxide you intend to use.
My friend informs me he is using 12% peroxide and 3 catalysts in his W model with his 300 gallon mixed reef with plenty of fish and that it holds approximately 1.5 litres.
The issue is one of control ensuring you add enough to be of benefit but to also stay at a safe dosing rate. I would suggest using a redox meter who help determine such. As you may know redox can vary greatly throughout the day and what might be a perfectly safe dosage say in the early hours might not be later in the day. Adding peroxide directly is always going to pose a risk with various corals either more or less susceptible to it's addition.
I would stay around 12% and use 2 catalysts and see how it goes. If you have nems then let them be your guide or if any invert shows a negative reaction but I would suggest the above won't be far away from ideal.
You could increase it to 12% I am sure depending on how much you feed and how heavily your tank is stocked.
You should be fine to go with it but watch your animals just in case.
