I’ve done 1 - 2.5 ml. of 30% food grade H2O2. 1ml is usually good for up keeping. 2ml if you’re trying to deal with an active problem. (can be applied every 3-4days).
At around 2-3ml you may start to burn the leaves a bit. However I did not notice any negative effects from it at all. As a matter of fact, the roots seem to love the extra oxygen.