A month or so ago, I noticed cyanno starting to pop up all over my tank. It seemed to prefer my 75 gallon tank, and my 40 gallon refugium glass. But I have also been noticing it on the rocks in my 180 DT. Tank has been set up since 2002. So a LONG time. Well established. Conventional wisdom would say elevated nutrients. My phos is .06 and nitrate is about 20 (somewhere between 15and 25 on the Nyos scale). Nitrates are slightly elevated, but by no means obnoxiously high. So I turn up my skimmer and start skimming wetter. This does nothing. In the meantime, I do an ICP test. Results say everything is normal, except potassium. Test says K is 316. Pretty low. So I start dosing K. Problem is, I can’t get it above 370 (Salifert kit). So I start dosing twice a day. Still waiting to see if I can get it to increase more. Well today, I notice 90% of the cyanno is gone, mostly replaced with a green turf algae. So I’m wondering if there is a relationship between cyanno growth and low potassium. Now I can’t say for sure that dosing K reduced my cyanno, but it sure seems too coincidental to be ignored. Like gone within days of dosing K. And that has me wondering if perhaps conventional wisdom is not so conventional.