24/7
Let's be realistic here. Algaes are very simple plants. They do not need a dark period. period.
There is always some discussion about a plant's light cycle versus it's dark cycle. There are two cycles in a photosynthetic arganism the photosynthetic cycle and the respiration cycle. Respiration occurs 24 hours a day at the cellular level in plants the same as it occurs in animals. The photosynthetic cycle occurs when there is . . . LIGHT!!
There is no reason that 24 hour lighting would be detrimental to an algae. Think about the lichens (read algae) that are located above the arctic and below the antarctic circles. Thes undergo time periods of 24 hour lighting and grow just fine.
On to the animals . . . with a well-planted refugium there will always be ample areas of darkness for pods etc. to hide in. But guess what? In the abscence of pred
ators the darkness is no longer needed. I have a refugium lit with over 6W per gallon of PC lighting and the pods population is tremendous. Even the bristle worms can be found sliding around on the surfaces of the macros.
I used to live right next to the pioneer seed world headquarters in Iowa. They had large greenhouses lit up like the sun with 1500W metal halides. They were over a half-mile from me, but you know how I knew they were there? They were lit up 24/7.
But hey, everyone is entitled to thweir own opinions and the ultimate decision on how to run one's tank always rests with the owner. Just wanted to share some of my botany from college.