top max is a mix of humic and fulvic acids. The humic acids help the root system while also improving the soil, enhancing the plant and making it more resistant to pests, root rot, and much more. Meanwhile, the fulvic acids improve photosynthesis. They recommend starting with 1 ml at the beginning of flowering and then increasing to 4 ml per liter. I recommend 2 ml from seedling to harvest; I also use humic acid to germinate seeds... it's not a PK booster because it doesn't contain PK.