Cavan Allen

It usually appears when nitrates levels are out of line. More often than not, it means that they're too high. Fixing that issue and/or increasing phosphates slightly along with good co2 and a photoperiod not exceeding 10 or 11 hours does the trick. A little manual labor, patience and time don't hurt either.

BryceM

I've got it BAD right now in my 180g. My 46g is perfectly clean with sparkling-clear water. I'm suspecting too-high nitrates in the 180g. I recently cut back substantially on the dosing of K, perhaps too severely. Over time, despite constant WC's and constant nitrate dosing, the measured nitrate in the water column is creeping upward. Phosphates continue to be slightly low, if anything. I'll report back after a few weeks of lower nitrate dosing.

Cavan Allen

Higher phosphates will force the nitrates down somewhat.

BryceM

Cavan, I agree. I'm currenlty adding 1.5 ppm PO4 and 4 ppm NO3 three times per week after a 20% WC. I'm thinking of going to 2 ppm of each, but this really doesn't "sound" right, according to what I'm accustomed to. I might try adding a bit of K2SO4 first to see how the NO3 responds.

Cavan Allen

I currently add a 3:2 N to P formulation and it seems to be going well so far. That may be a tad much but it doesn't hurt anything either. I see a little bit of haystack but if I back off just a little it will go away; that algae is a useful indicator for exactly how much P you need.