Thanks for the reply...
These are the lights that I use; I have 3 of the 11w ones, 2 whites and then I've put a 9w actinic in the middle one: Arcadia - ARC-POD
I'm running RowaPhos and have been for about 6 months, it didn't improve anything; as soon as I get the algae off it returns within about 3 days again (green hair algae all over the rocks is the main problem, not much on the glass).
When I say "low" phosphates they're classed as "barely on the scale" by my LFS
...but it could be that the algae could be consuming them all, that's why they return a zero reading?
Water parameters: pH 8.2, amm 0, nit 0, nat <~3ppm, SG
1.024, temp ~27°C.