not much, did 3 grows with it didnt notice it did anything bad.
had a problem one time when i put in too much bacteria they stabilised ph to 6.4 not really a problem but i wanted it lower. they are super cheap
i use it just as protection from bad bacteria last year my water was allways 27C+
and myco i used in soil it worked great allways. does it do anything in water i dont know but they have kelp in it soo growth hormos at least work...