I also use kool-bloom with my flora-nova but you don't need very much at all, flora-nova has a lot of the stuff cool bloom has in it allready. As was said, GH stuff is chemicals but flora-nova has more natural ingredients in it. It has the molasses and such. If you do go with it be warned, it is very, very concentrated, just pick up a bottle of it and a bottle of pure blend, you can feel the difference, so be careful.