I understand what you are saying and agree completely but this tank has been great on the water balance. My NO3--around 5ppm and PO2 0.2ppm so im not sure what is causing it.
Forget levels. When you have algae, that's all the test you need.
It's a process of elimination to figure out the cause....never that hard though.
Overstocked?
Overfeeding?
Lack of flow?
Buildup of detritus in rocks?
Buildup in sand?
Nutrients from makeup water?
It's always one or more of these kind of things.
What have you checked so far?
-Matt