It is not mandatory necessarily, but i would not ever go without it. Most people i feel will agree with me who have used co2. Your going to need to get a regulator, needle valve, and maybe a solonoid. Use all 10k bulbs, actinics have not proven to show any benefit to plants. I would wait for more flourite. But i have used a 50/50 mix and it does well, i just get paranoid (What if it could be better).