Here's a recent question about photoperiods for growing plants in a freshwater refugium:
"BTW, what do you people suggest for a photo period? I think most of the reefers run lights on all the time. They mostly grow multicellular algae. Would higher plants need something different? I am currently leaving the lights on 24 hrs."
If you can spare the electricity, I would keep the lights on 24 hr per day to maximize plant growth in your refugium. I see that you have floating plants, so CO2 won't limit the growth of your plants. Plus, with 45 tanks filled with guppies hooked up to your system, the plants in your refugium will never want for nitrogen and other nutrients.
This isn't the first time a question about the effect of photoperiod on plant growth has been asked. Several times I've seen answers (even from aquatic botanists!) that aquatic plants need a "rest period". This implies that aquatic plants somehow need to recover from a hard day of photosynthesis. Well, the following paper says otherwise.
REFERENCE: Pilon J and Santamaria L. 2002. Clonal variation in morphological and physiological responses to irradiance and photoperiod for the aquatic angiosperm Potamogeton pectinatus. Journal of Ecology 90: 859-870.
It took me a couple days to decipher this incredibly comprehensive paper. The bottom line is that Potamogeton pectinatus, which is a rooted aquatic plant with worldwide distribution, grew better with a 22 hr daylength than a 13 hr daylength. This was true for 3 different strains of the plant species whether it was exposed to low intensity or high intensity light. The increase was dramatic and statistically significant in all cases. For example, a P. pectinatus strain from Russia increased its biomass from 180% with 13 hr daylength to 300% with 22 hr daylength when it was grown under high light intensity. When it was grown under low light intensity, it increased biomass 90% under 13 hr daylength and 230% under 22 hr daylength.
The investigators found no significant difference in plant growth for plants exposed to 13 hr and 16 hr daylength. Thus, we must not split hairs here over a 3 hr increase in daylength. Nor do I recommend that hobbyist keep the lights on in their aquariums for 22 hr/day. My point is that aquatic plants keep photosynthesizing and growing as long as the lights are on.
"BTW, what do you people suggest for a photo period? I think most of the reefers run lights on all the time. They mostly grow multicellular algae. Would higher plants need something different? I am currently leaving the lights on 24 hrs."
If you can spare the electricity, I would keep the lights on 24 hr per day to maximize plant growth in your refugium. I see that you have floating plants, so CO2 won't limit the growth of your plants. Plus, with 45 tanks filled with guppies hooked up to your system, the plants in your refugium will never want for nitrogen and other nutrients.
This isn't the first time a question about the effect of photoperiod on plant growth has been asked. Several times I've seen answers (even from aquatic botanists!) that aquatic plants need a "rest period". This implies that aquatic plants somehow need to recover from a hard day of photosynthesis. Well, the following paper says otherwise.
REFERENCE: Pilon J and Santamaria L. 2002. Clonal variation in morphological and physiological responses to irradiance and photoperiod for the aquatic angiosperm Potamogeton pectinatus. Journal of Ecology 90: 859-870.
It took me a couple days to decipher this incredibly comprehensive paper. The bottom line is that Potamogeton pectinatus, which is a rooted aquatic plant with worldwide distribution, grew better with a 22 hr daylength than a 13 hr daylength. This was true for 3 different strains of the plant species whether it was exposed to low intensity or high intensity light. The increase was dramatic and statistically significant in all cases. For example, a P. pectinatus strain from Russia increased its biomass from 180% with 13 hr daylength to 300% with 22 hr daylength when it was grown under high light intensity. When it was grown under low light intensity, it increased biomass 90% under 13 hr daylength and 230% under 22 hr daylength.
The investigators found no significant difference in plant growth for plants exposed to 13 hr and 16 hr daylength. Thus, we must not split hairs here over a 3 hr increase in daylength. Nor do I recommend that hobbyist keep the lights on in their aquariums for 22 hr/day. My point is that aquatic plants keep photosynthesizing and growing as long as the lights are on.