Cause of my green spot algae
I've been trying to work out the root cause of the gsa I get building up on my glass and occasionally leaves. I've got a 200L low tech moderately planted tank with mainly slow growers. I've got a 15w light on for 7 hours a day. My tap water parameters are hard, with zero nitrates and about 5ppm phosphates. I dose excel for a CO2 substitute and easy life for micronutrients. After 2 weeks without a water change my phosphates and nitrates are still comparable to the tap water.
From the other posts I've found on gsa, a low phosphate is often the culprit - I was wondering if a low nitrate could also contribute to it?
Many thanks in advance