I've heard something similar that algaes in darkness reverse CO2/O2 cycle and go into asexual reproduction causing green tinged water throughout system. I am willing to place a timer and reverse the cycle to lighting of my display, or, the 2 hr cycle mentioned above. I am currently running chaeto in a eggcrate sandwich.I created.
Yeah, that sounds familiar. About the calurpa, there are two kinds that I'm aware of. The kind with little balls all over it and the kind with little flat pads all over it. I've heard flat pads type is desirable, balls not so much, for sexing reasons as well (more speculation). I always just use cheato as well. It grows fast, it's hardy, I've even traded it for store credit at the lfs. My original theory was, leave refugium lights on all night and cheato will photosynthesise all night. Thereby, oxygen levels remain stable keeping pH up. It made a small dent in the problem. I think it would take a much larger refugium and much more cheato to really solve the overnight pH issues. Even a big a** skimmer didn't do much to help.
Added note: I'm beginning to think that running a skimmer AMD a refugium might be counter productive.
One thing is certain. I've never been equally successful on two different tanks, with one method. Know what I mean? Basically, I don't think that there is a single method of reef keeping that works on all reefs across the board, even if both tanks had the same exact livestock (never tried it that though). Not sure why that is, factory variance on equipment maybe?