I would doubt it, since the recommendation for reef tanks is usally 72-78*F, but two questions: why keep it that low when the trend seems to be around 78*F? and how are you keeping it that low? I mean, the trend towards keeping tanks closer to 78 is probably just because of the MH lighting that most of us use. So for most people, 72 just isn't realistic. But as long as it's consistent, I don't know of any reasons why it wouldn't work.