GFO question for the experts

[Crush Coral]

I have 1 1/2 cups of Rowaphos in my phosban reactor. My po4 is .06 4 days after putting tye Rowaphos in the reactor. I wish to test if the Rowaphos is absorbing po4 or not. Does gfo absorb po4 fast enough that I can test the tank water and then the water coming out of the reactor and compare the two readings or does gfo not absorb po4 fast enough for that to be a viable test? Thanks.

 

[scooter31707]

Give it some time. It's just not going to happen overnight. Give it about a week and test.

 

[dkeller_nc]

Honestly, probably not. I often see this recommendation for determining when GFO is exhausted (testing the tank water and the water coming out of the reactor). The problem is that we're generally testing for very low levels of phosphate (in the parts per billion range, or at most low parts per million), so test variation can make it troublesome to determine whether the GFO's actually exhausted.

The other issue is channeling; depending on how much media you have in the reactor, its particle size and the flow rate, a decent portion of the incoming water may not "see" the GFO before it exits.

Bottom line is that I'd test for PO4 every couple of days. If you don't see the tank water's concentration going down substantially (or rising), it's pretty safe to assume that the GFO is exhausted.