In my opinion, it's best to have circuits added if there is room on your breaker panel for them. I was running a 75g reef with halides, closed loop and everything else and I had to use two different circuits to keep the breakers from tripping. I think it usually occurred when the halide ballasts clicked on. For the 240g I started setting up, I ran two circuits to support it in addition to the one that was existing in that room to make sure I didn't have any issues.