Join Date: Jul 2010
Location: Outside Philadelphia, PA
Strictly speaking, you don't really need to use CO2 at all. However, once I converted to it, there was no looking back.
I don't use a planted refugium, but if I did, I would still use CO2. It solves a lot of problems, especially with algae control.
You could always skip the CO2 additions for now, and see how you make out. If it works for your system, that's great. If not, it's easily added later.