Hydroguard is supposed to get rid of/protect against algae. I put it in every res change and haven't had any problems with it until then. It was also the first time I added full strength nutes.

Also, I've since switched to flowering nutes (Pure Blend Pro 2.5-2-5) at half strength along with the Hydroguard, Hygrozyme, SuperThrive and Liquid Karma. The LK turned my res black as soon as I put it in, and it seems to leave a gritty looking residue on my roots and it settles on the bottom of the bins and the res. Is this normal?