Rice Reef's 120 SPS Reef Tank

[Rice Reef]

This morning's po4 reading was .25... It went up. After a strong cup of coffee I traced back to everything that i did in the last four weeks, including the water changes... could it be a defective Hanna or the RO unit? I don't recall checking the RO water lately... I had just made a fresh batch this morning... The TDS read 016. Tested the tap water... .019... Then it hit me... I forgot to change the RO units membrane! To be certain I took it to a LFS and had the tap water and the tank water tested and it came up with very similar results. The last four week of water changes was all for nothing. I could have prevented the build up of po4 had I used the TDS meter.
Will be making a large batch of RODI water tonight ( with a new membrane).. . The lesson learned is to not assume the water is po4 free even though the last batch was. I will put off in using GFO at this time and try reducing the po4 naturally. Will be testing the po4 regularly for now.