I set my timer on my lights to have 4 shorter dark periods instead of one dark period. But then I got to thinking that it might impact the growth of the algae. Does the length and number of dark periods affect growth?
Multiple shorter periods are good when you are starting a screen from scratch and are having issues with growth getting started or filling in. Once you have established growth, I'm not sure how much good it does to split up the photoperiod. I don't think it can hurt, as long as the total "on" time per day is the same. If you are getting yellow growth after a period of decent green, adding in the intermittent dark period can help. In this case though you would not add hours on either end - you would reduce the photoperiod by going dark in the middle of the current cycle setting - because yellow growth indicates too much light and/or for too long in comparison to nutrients delivered. If possible, increasing flow should be the first attempt though, if that doesn't work, then nutrients are just less available overall.
I always worked on the assumption that algae has evolved to take best advantage of the natural day/night cycle so one off and one on period per 24 hours would probably work best. But recently I did split the cycle into two each per 24h and believe that there has been an advantage, although probably not very significant. Could it be possible that algae growth (or at least nutrient uptake) is at it's peak during the "wake up period", (i.e. after sunrise) and that by creating multiple artificial sunrises during a 24 period, you can gain an advantage filtration wise?
