Carbon and GFO?

[ROMABE]

Im getting In to the Hobby got my self a 20G water-box I want to run Carbon and GFO for my chemical filtration together however I don't know the measurements? can some one help, THANK YOU

 

[Biglew11]

you don't need and should never run gfo unless you have high phosphates. you do not want phosphates at zero. they should be around .03 to .1 ppm to measure this you will want a hanna ulr phosphate checker.