finally got around to checking my source water

[quarryshark]

Been battling hair algae and cyno, not horrible, but annoying. Was doing everything by the book and running phosphate sponges galore but could never get my PO4 below .25 for very long.
Since i had recently changed the filters on my r/o unit, I never until last night check it. Well lo and behold the PO4 of my r/0 water is guess...
You got it .25.
Does this mean I need to change the membrane? I believe its the only thing left.
I am take a water sample to my lfs tonight to test for TDS.

 

[quarryshark]

Just FYI in case someone in the future is looking for answers to a similar problem.
Did a little reaserch and because I was using a 2 stage RO unit, a bit of PO4 was leaching into my water. Added a deionizer stage to the unit, ran it and tested the water. The PO4 was 0. Manybe this will finally be my solution for the hair algae.
Wasn't the membrane after all, cheaper fix too.