hey tang my nitrates are undetectable and phosphates with colorimeter are .02. I still have algea on my rocks I am guessing it is bound up in the rocks and until it is all unbound or covered over by coralline it will be useable by algea to grow even though it isn't available in the water column. I have been using prodibio around 2 months now and still have algea. it may just depend on how far off your tank was when you started. of course if his bulbs are shifting we could throw that all out the window.