Inexplicable algae: 8 month-old 500-litre tank, sump and protein skimmer. Water is crystal-clear. I've just measured Ph 8.0 (I've added a bit of buffer to get back to 8.2), NO2
0, NH4 0, PO4
Fish are lively and in perfect health, I feed them a varied diet every other day and the protoreaster gets a mussel once a week.
The skimmer bubbles out about 50cc (a small coffeee cup) of black water a day.
BUT over the last 2 months I'm getting ever-increasing algae (green, brown and cyano
on the sand). I've siphoned, stirred, prayed, to no avail.
Any ideas/suggestions would be most appreciated.