P04 Spike after adding Rowaphos? Is this real life?

[Bustyraker]

I have a heavily stocked SPS tank. I carbon dose with Nopox and I have always had trouble controlling brown algae on glass so I decided to give rowaphos a try about a month ago. Before adding rowaphos my Po4 measured .02 ppm with my Hanna ULR Phosphorus Meter. I started with 1/4 cup of rowaphos just to be safe because Ive read that using phosphate absorption media while carbon dosing is a no no. After a few weeks I checked my po4 again and it had risen to .03+ even after running rowaphos. Keep in mind that I have stopped feeding corals and have cut down on feeding fish since I started running running rowaphos. At the beginning of this week I decided to add more rowaphos durring a water change and upped the amount to 3/4 cup. Today I tested .113 ppm!!!! Im not sure whats going on here but I dont like it. Could the combination of carbon dosing and rowaphos be pulling po4 from the rocks? My rocks are fairly old, 6 years or so and Im sure theres all kinds of nasty stuck down in there.

Parameters are as follows.

Nitrate 0 ppm Salifert
Phosphate .113 ppm Hanna
Alk 8.1 Dkh Hanna
Calcium 425 Salifert
Potassium 420 Salifert

105 gallon display with 25 gallon sump
SRO 3000 skimmer

 

[Randy Holmes-Farley Verified Community Expert]

Adding more Rowaphos (GFO), assuming it was new and not already used, didn't itself make the phosphate rise. Either it is testing error, or something else caused it.