I have little doubt that if I added co2, the problem would go away, but I'm not ready to go that route yet, for logistical reasons
It's a 20 long with 20w of FloraGro lighting.
Nitrate: I keep in the 5-15 range
gH: 100 ppm or 5.6 degrees (if translator worked properly)
kH: 65 (translator didn't offer a degree equivalent)
Phos: < 0.5 - like, about 0.25 or less (barely detectable)
Flourish Excel - single dose added daily
Flourish Trace - recently started adding once weekly
Flourish Iron - started adding twice weekly (see note below)
Flourish Potassium - started adding with iron to help with iron uptake.
Flourish - Once weekly
I've seen a reduction in algae since starting the above regimen, but not total elimination. Plants were showing signs of iron deficiency and iron reading was zero.