I had to Google paraquat. I've heard it before, but could not remember the context. Thanks again to the internet I found it. If you can, it's always good to buy local. Oh...I had HA algae and I just went the shot gun method. I tried doing one or two things, each for a couple of weeks with no noticeable change. So I did all of the following and it ended it. 1) Pulled/scrubbed HA 2) Filter sock (replaced weekly) 3) Reduce feeding 4) Reduced light hours 5) New lights 6) UV 7) Denitrator 8. GFO 9) Kalk 10) Increase volume of weekly water changes I did all of it simultaneously, so I have no idea which one or which combination ended it.