Why, do you have a manganese deficiency? if so what makes you think so? Im pretty sure most fertilizers have some manganese in them, i think its in tap water too, im not sure. I have no Idea what the best type to use or best chelated would be, I dont understand...are you gonna get lab grade manganese and make your own fertilizer or something??? A health food store? I use sensi two part and it has Manganese EDTA, and Manganese Proteinate, a total of 0.06%, and my plants dont seem to have any deficiencies.