Depends on the amount of minerals in the fertilizer, you need to start from this. If it says to add 2 ml per 1 liter of water, then 1 ml will be enough for the first time, then you can gradually increase the dose of fertilizers. For example, I had fertilizers from Advansed nutrients, I added a full dose for auto like for photoperiod and everything was fine, but the amount of minerals per 1 feeding is not very large, if you look at the instructions.Therefore, it is better to add 1 ml and see how the plants react. And then, starting from about 4 weeks, you can increase the dosage.