If you don't want to run a reactor for GFO, you can use a liquid alternative called Phosphate Control (or Phosphate Rx) by Blue Life USA. It turns the phosphate to a solid to be exported via a fine micron sock or by skimming it out overnight.
I like a reactor for active carbon filtration, and wouldn't run it any other way.
Carbon and GFO are two totally different products, the former works for a few days until it is spent, while the latter can last two or three months.
