I do the same as 29reef. I started dosing vodka a couple months ago due to an algae problem that I could not get on top of with just GFO and water changes. I read somewhere about taking the reactor off line when dosing a carbon source, but it was more or less a suggestion. Not really mandatory from what I understood. I have left mine running, and my tank looks amazing compared to a few months ago. Maybe one of the more seasoned SPSers might chime in on this one.