Actually monopotassium phosphate is in most nutrients. There is nothing wrong with it as an ingredient in a nutrient blend. But once it's repackaged and given some cool name and called a bloom booster it is nothing but a money grab by nutrient companies. Plus it's not needed since any decent nutrient line already has adequate amounts. If you need to add a bloom booster then the base nutrients being used are not providing everything a plant needs. This is mostly by design as it's a way to sell another product and increase profits. I use a three part water soluble nutrient. Part C which is used in flower is just monopotassium phosphate. I've been using this nutrient for well over a decade in soil, hydro, and coco. Everything is there and no need for any additional repackaged MKP with a fancy label called a bloom booster.