Photoperiod with Co2 + medium/high light

No, you will not have to change your photoperiod. It's actually a good idea to not make too many changes at once on a stable tank. That way, if you get results you're not happy with, you know what changes led to those results which can better help you make adjustments.

Having more CO2 than the plants can use due to lower lighting is not a problem. The problem most people run into is the opposite: not having enough CO2 due to increased lighting.

So you can add your CO2 and leave your lighting as it is. Once you feel comfortable, you can increase your photoperiod a little to see how that affects things. If all is going well, you can increase your photoperiod even more. Keep doing this until you get the photoperiod you want or you run into problems. Either way, you'll be able to track what changes created what affects which makes it easier for you to know what other changes you need to make if things go wrong.

Shutting the CO2 on and off should not have any harmful affect on the solenoid. Some people, like me, run their regulators from a pH controller which turns the solenoid on and off multiple times each day.

It isn't natural for the lights to go off in the middle of the photoperiod, but the plants can adjust.

The only issue you'll need to be concerned with is getting the CO2 raised to high levels by the time the lights go on and then back to low levels when the lights go off. There's usually a lag time which will be compounded since you'll be doing it twice. You'll just have to play with it until you figure out when to turn it off and back on to get the levels right.

As far as acclimating the plant to different photoperiods, I wouldn't worry about that. Just change them to whatever photoperiod you want and be done with it. They don't need a slow transition.

frrok said:

Ok. Thanks for the advice. I guess I can add the new low light at a high level so it's so much of an abrupt change then slows lower it. Then I guess I can keep my siesta period or no? Will shutting the co2 on and off daily have an affect on the solenoid functionality overtime. That's really what I'm asking. I'm not sure that it's natural to have the light go on and off. I would have to acclimate the plants back to a straight schedule.

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First off, do you understand a siesta period isn't a complete cessation of photosynthesis, just reduced photosynthesis ? Like what would be created on a partially cloudy day or during a rain storm

There's no sound reason (writ in stone) that co2 needs to be shut off. Nature doesn't stop at night. Some sources of co2 come from chemical processes taking place in ground water or subsurface water before entering into the stream, lake or pond. These processes don't stop at night. Bacteria still metabolize at night releasing co2. Now if you chose to inject 24/7 you'll do so at a reduced rate then you'd do if you use a solenoid on off. This advice is given from decades of experience plus reading science articles on the subject. Like the one linked below

Complexity said:

Shutting the CO2 on and off should not have any harmful affect on the solenoid. Some people, like me, run their regulators from a pH controller which turns the solenoid on and off multiple times each day.

It isn't natural for the lights to go off in the middle of the photoperiod, but the plants can adjust.

The only issue you'll need to be concerned with is getting the CO2 raised to high levels by the time the lights go on and then back to low levels when the lights go off. There's usually a lag time which will be compounded since you'll be doing it twice. You'll just have to play with it until you figure out when to turn it off and back on to get the levels right.

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Agree.

A reason too run co2 24/7. It's really not necessary to get levels low before lights out. Many bodies of water are supersaturated with co2.
Carbon dioxide supersaturation in Florida lakes

http://www.plantedtank.net/forums/showthread.php?t=153685