dwalstad Moderator

Join Date: Apr 2006 Posts: 2,353

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Lighting-Siesta & CO2



I have brand new data for you on lighting and CO2. It firms up my argument for the Siesta Regimen, that is, to give plants an "afternoon nap".



Below is a figure showing CO2 measurements on my 50 gal tank over the course of a day. The day starts at 7:00 AM when lights come on, so that is TPt 0 (Time Point zero). As you can see, CO2 is rapidly depleted over the next 5 hours. It drops from 5 mg/l at TPt 0 to 2 mg/l at Tpt 5 (Noon). This can only be due to plant photosynthesis.



If I leave lights on continuously all day for 12 hr to 14 hr, CO2 continues to decrease and level off at 1 mg/l and stay there throughout the afternoon. This is not ideal. It means plants are competing for not much CO2 all afternoon. Since algae is better at getting CO2, it gives algae an opening.



However, the Siesta totally changes things. At noon, plants get a 4 hr nap (TPt 5 to TPt 9). Overhead lights are off. Even though this tank is near a window, it looks like window light isn't enough to keep photosynthesis going. So you see a rapid rise in CO2 during "nap time".



When nap is over and lights come back on again at 4:00 PM (TPt 9), the CO2 has bounced back to 4.5 mg/l. This is perfect! Plants now have some CO2 in the afternoon to use for there photosynthesis. As you can see, plants are taking up CO2 almost all afternoon and evening. CO2 decreased from 4.5 mg/l to about 3 mg/l at 9:00 PM (final TPt 14).



The Siesta Regimen is ideal on several levels:

Saves electricity. Lights are on only 10 hr instead of 14 hr (with all my tanks this saves me $6/month) Gives plants the nice, long photoperiod that they need to do well (I discussed this earlier with documentation; photoperiod should be at least 12 hr) Fits in with plant physiology and CO2 dynamics (discussed here) Probably helps with algae control I repeated the CO2 measurements on 3 other tanks. Same lovely pattern you see here.



I am submitting a full discussion to The Aquatic Gardener for publication next year. However, I wanted APCers to see this new data showing how sweet the Siesta Regimen truly is.



Now, all my tanks (with submerged plants) are on Siesta Regimen. Hello Folks,I have brand new data for you on lighting and CO2. It firms up my argument for the Siesta Regimen, that is, to give plants an "afternoon nap".Below is a figure showing CO2 measurements on my 50 gal tank over the course of a day. The day starts at 7:00 AM when lights come on, so that is TPt 0 (Time Point zero). As you can see, CO2 is rapidly depleted over the next 5 hours. It drops from 5 mg/l at TPt 0 to 2 mg/l at Tpt 5 (Noon). This can only be due to plant photosynthesis.If I leave lights on continuously all day for 12 hr to 14 hr, CO2 continues to decrease and level off at 1 mg/l and stay there throughout the afternoon. This is not ideal. It means plants are competing for not much CO2 all afternoon. Since algae is better at getting CO2, it gives algae an opening.However, the Siesta totally changes things. At noon, plants get a 4 hr nap (TPt 5 to TPt 9). Overhead lights are off. Even though this tank is near a window, it looks like window light isn't enough to keep photosynthesis going. So you see a rapid rise in CO2 during "nap time".When nap is over and lights come back on again at 4:00 PM (TPt 9), the CO2 has bounced back to 4.5 mg/l. This is perfect! Plants now have some CO2 in the afternoon to use for there photosynthesis. As you can see, plants are taking up CO2 almost all afternoon and evening. CO2 decreased from 4.5 mg/l to about 3 mg/l at 9:00 PM (final TPt 14).The Siesta Regimen is ideal on several levels:I repeated the CO2 measurements on 3 other tanks. Same lovely pattern you see here.I am submitting a full discussion tofor publication next year. However, I wanted APCers to see this new data showing how sweet the Siesta Regimen truly is.Now, all my tanks (with submerged plants) are on Siesta Regimen. Attached Thumbnails Monrankim and SpeedyTheBetta like this.