Are you mixing the carbon and phosphate media together in the same reactor? If so, they each should be run in a seperate reactor since the carbon should have more flow thru it than the phosphate media.
But to answer your question, hydrocarbon by 2 Little Fishies is a very good carbon and there is no real reason to change to a different brand....unless you are paying a high price for it.
ROX 0.8 from Bulk Reef Supply would be a excellent choice if you decided to use a different brand carbon.
ROX 0.8 High Performance Carbon - English
BRS also sells GFO
pellets which work great in a phosphate reactor.
Bulk Pellet GFO (Phosphate Remover) - English