reeftivo
Skim junkie
what kind are you using? I got one of those green handheld Hanna Phosphate Checkers for Christmas -- tested it 4 times, and it reads 0.00 every time. I just feel like that cannot be correct (especially given that i have some algae growth, not to mention reasonable SPS coral growth), but who knows.
Was using the cupel version LR hanna photometer. Now use the martini MI-412. Both are within .04mg/l. Is your algae primarily on the sand and rock? It is very typical to have 0 readings and still have algae on rock and sand. It would be bound in both, and the algae feeds off it directly, thus giving you a false reading in the water column. Do you dose Kalkwasser? Kalk is reported to bind phosphate and distribute it on the rock and sand and if algae is present it still can utilize the phosphate directly.