PO4 and RO water

[ellisz]

Has anyone tested their RO/DI water for PO4? I have had a cyano issue for awhile now and I tested the RO/DI water using a Aquarium Pham. Phosphate test and got a reading of .5.

I have recently read that a cheap GAC filter can leach phosphate into the water. I have one of the popular units off ebay and get a TDS of 0-1 from the 100 gpd 5 stage system(I don't use the 6th stg carbon)

Any thoughts?

 

[malkore]

RO water shouldn't contain phosphates. I honestly haven't researched RO units at all, so I can't comment on that.

What I will say is validate your results with a better test kit: SeaChem, Salifert, or a LaMotte. Phosphate test kits can be quirky.

 

[lando]

Might just be time to change the filter membranes. I believe the PO4 is taken out by the DI portion, maybe somone can confirm this?

 

[quarryshark]

Yes, it is taken our with the DI unit. I added one to my RO and it solved the problem for the most part. I am getting a little on my glass, but I can deal with that. Beats the sheets that used to be on my rocks.
Ellisz, sorry you are having so much trouble with this.
Try running kents PO4 sponge. Even with the changes I made, I still run it once a month.

 

[ellisz]

Quarry, How long do you run the sponge and how much do you use? I bought some of the Kent PO4 sponge and ran it for a couple of days. I assume you have to discard it or recharge it? I just put about 4-5 tablespoons in a media bag and dropped in my sump under the drain line.

Maybe I will drop in a new DI filter and see what happens.