How about the carbon you get at walmart. It is made by Marineland...heck it is the same container as black diamond. I've been using it for over a yr and works great. It's called Aqua-Tech ..900ml is something like $3.50 retail. Maybe we can get bulk of this stuff. I'm in if it is cheaper and same stuff...
I have been using petcetra. its bulk carbon so it needs to be rinsed WELL before use. no problems with it. someone will need to give me a strong case to spend alot on carbon.