You can. I think that its really important during treatment. Lots of people have used this with good results, but I understand how you feel. I just poured an algae removal in mine LOL. You know, speaking of chemiclean, my lfs uses it so often, I dont think it works for them anymore. Their tanks are full of cyano. And its funny cause the other day when i bought the algefix, they said hey,we just got this new stuff in called chemiclean LOL.