Changing GFO

[Koddie Doo]

How do I know it is time to change my GFO?

[vitodog]

I change mine when I test for phosphates and see an increase. Also, it depends on what your phosphate levels were when you started the GFO. If your levels were very high to begin with, you might have to change the GFO more frequently. If your levels were very high, the GFO exhausts itself rather quickly.

[droth335]

I use the BRS calculator to determine the monthly amount to use and then change it out every month. I prefer this than to wait for PO4 to rise although I would certainly change it if it does rise prior to the end of month. Here is a link to the calculator:

http://www.bulkreefsupply.com/store/reef-calculator#GFOCalculator

[Randy Holmes-Farley]

How fast it depletes depends on how much phosphate is in or added to the water, and how well water is forced through it. It can easily be depleted in an hour or two if the phosphate level is very high.

How soon to replace it also depends on what your goals are for it in terms of phosphate levels in the tank.