Timing Lights and Photosynthesis Periods

[Garrett Johns]

Hey guys! I’ve got a Finnex 24/7 light that I’ve been using on my 55 gallon for about 7 months now. I was watching some old livestreams and heard Cory mention that plants need a time to rest and release co2 before photosynthesizing again. I’m wondering if my 24/7 light being on all the time (it cycles through a night and day mode constantly) will hinder my plant growth? Would it be better to have the light turn off completely, or does it matter? Thoughts? 

[Streetwise]

The symmetrical activity to photosynthesis is plant respiration. @Daniel has provided commentary on this topic which has been very useful to me.

[Koi]

I'm not sure how much having a 24/7 mode will hinder your plant growth but personally I like having a good amount of time for the plants to "rest".

At least from my very general understanding how plants grow, the way I understand it is that plants photosynthesize during the day creating their food so that that it can "eat/grow" during night. I'm not entirely sure how correct that statement is but I've definitely seen this occur with some of my stem plants.

This is somewhere near the middle of my light cycle. I can't seem to find a picture where it was at its peak stage of photosynthesis, but this is close enough. Usually the petals of the rotala are completely flattened out trying to absorb as much light as possible.

Here it is an hour before light goes off and the petals are starting to close off.

30 minutes before lights off

This is I think is 4-5 hours after light has shut off. I couldn't find a picture at lights off when the petals fully closed but hopefully you can see the growth

[bettatester]

You definitely want the plants to have a dark period and a consistent one at that. My understanding is that plants make food during photosynthesis and use the food made, therefore respiring, during times of rest. So, they can photosynthesis all day long, but they cannot use this food to grow until they are in the dark. 

[Streetwise]

With a pH probe, you can see the pH change during both photosynthesis and respiration.