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.

[Werbo]

Have you tested the tap water for PO4 or just used the TDS?

I'd do a Hanna PO4 test on the tap water.

Have you ever flushed the RO membrane? I'd try flushing the RO membrane before replacing it.

[Delphinus]

I thought I read somewhere that the Hanna checkers for phosphate don't give correct readings on freshwater. Having said that I can't seem to find the link where I read that, so I'm not 100% sure. I guess it can't hurt to have a new RO membrane regardless..

[Rice Reef]

Originally Posted by Tyler Werbowski

Have you tested the tap water for PO4 or just used the TDS?

I'd do a Hanna PO4 test on the tap water.

Have you ever flushed the RO membrane? I'd try flushing the RO membrane before replacing it.

Yes, I did... First test was a triple zero, second test was .028 and third test was .017... That was what prompt me to question the Hanna po4 tester.
The old membrane was due for a change. I had forgotten to do so in the summer.

Originally Posted by Delphinus

I thought I read somewhere that the Hanna checkers for phosphate don't give correct readings on freshwater. Having said that I can't seem to find the link where I read that, so I'm not 100% sure. I guess it can't hurt to have a new RO membrane regardless..

I don't know much about that but after testing it with the Hanna you may be right about that. Have a new one, in fact, I upgraded to the deluxe puratek... No more guessing and forgetting... Guess I'll be keeping the old one ( which is like new) for drinking only.
Making new water right now. TDS: 000.