FWIW
Although many light their refugiums 24/7, there are equally as many who employ the "reverse lighting" system. That is, the refugium is lit opposite of the display tank. When the display lights are on--refugium off. And vice-versa. This is much more natural IMHO. The thinking behind the 24/7 lighting is that it will keep the calurpa growing in the refugium from going asexual.
HTH
Hermit