I feel your pain here, i had just set up my tank and added co2 when greenwater bombed me. After 2 weeks of various methods including blackouts, intensive waterchanges, and even a flocculent in desperation, nothing happened. I was about to give up when I finally got the fix. Hydrogen peroxide will fix your tank in a matter of days. Just be careful with any vascular plants as they tend to be more sensitive. I poured 1.5 mL per gallon for four days and it was gone (make sure you dont do a major waterchange in this time). Good luck!!!