Thanks for all the replies -- I'm pleased to hear so many people seem to have success using the split photo period. Getting back to my original question, I'm wondering about whether there is such a thing as "too dark" for the siesta. It seems like many of the people employing the method have their tanks next to windows and are therefore getting a fairly good amount of natural light in the middle of the day. My tank is in a finished, partially-underground basement room where the windows are at the ceiling, above the tank, so the room gets *some* natural light, but it's a pretty dimly lit room when the lights are off. On a dark, cloudy day I can barely even see what's going on inside the tank when the light is off. Does anyone think this is "too dark" for a siesta?