I have read several postings about light timing for refugiums. I read "light opposite to the main" I've read "light 24 x 7". Which is better? And why? I have 120 gal main tank and CPR 18" HOB refugium. :notsure:
I think you're referring to an algae scrubber. In my opinion Lighting 24/7 will give more algae growth but not twice as much as 12 hour lighting. I did a few experiments and the amount of extra growth seems to depend a lot on the type of algae you have. Caulerpa grew about 15% more for me with 24/7 lighting vs reverse display lighting. Chaetomorpha did a lot better.
For me the double electric bill and reduced bulb life didn't make it worth it for the small amount of extra growth. Your situation may be different.
Cyanobacter does best in low oxygen/high lighting environments. If you're getting cyano in a refugium it usually because the waterflow is too low. Most new refugiums get a cyanobacter bloom because they are the first to colonize new surfaces. If your refugium is very new then it may just be time before beneficial bacteria crowd out the cyanobacter.
My refrug did get a break out of red slime algea only in the refrug and not in the main tank I boosted teh flow in there and did red slime remover a month later loaded with all the right algea and doing very well.