Motor is correct. The other issue is they do not have the same adsorption rate so they should not really be mixed. However, it is good to put a little carbon in with the GFO which helps the GFO not turn into a "block" or a some what hard mass.
Pat they both have different size granules so they need different flow rates....it's very hard to keep the phosban tumbling and still have good flow through the carbon if they are in the same reactor....either use two seperate reactors like two TLFs or BRS dual reactor which is what I use with a MJ1200 pump and a flow valve...