I have searched around a little here and other sites. I found some info and made some assumptions based on logic.

I believe this is a very interesting topic and would like to have other add there input.

This is my Disclaimer:


Split photo period/"siesta" Pros/Cons

Pros:
-More consistent /higher CO2 levels in DIY CO2/non CO2 injected tanks(see note 1).
In a non CO2 injected tank or even DIY CO2 levels may bottom out during the mid day. Then the rest of the day they are struggling to get any/all CO2 that is available. Using the split period with 3-5hours of "siesta" will let the CO2 levels build back up since plants only uptake CO2 when the lights are on. So when the lights come back on they can continue growing at faster rates from the higher CO2 levels. Also the steadier CO2 levels when the lights are on should give plants the upper hand compared to algae that takes advantage of low or fluctuating levels.

-If you have low water movement in the tank, the siesta may also be a benefit as it will let plants and the water time to get more nutrients. If the water surrounding the plants is depleted. This could benefit any tanks that have low flow(even CO2 injected ones), but prob not as much difference in tanks that use substrate ferts.


Cons:
-Fluorescent bulbs wear out faster
Instant start/rapid start ballast that are used in fluorescent lighting use high voltage to get the bulbs running. This seems to be hard on the bulbs, harder then having them run for more hours. So using a "siesta" and having the bulbs turn on 2x per day and using the same total hours of lights on, will wear out the bulbs faster. Most people replace the bulbs before they die, due to spectrum shifting. It seems to me that the "startup" is part of the cause of the spectrum shifting as well.


Notes:
1:Not all non co2 tanks are the same. NPT(natural planted tanks) or similar that use some kind of "soil" for the substrate are very different from using a regular substrate. The main reason is that in a "soil" tank, the soil and decaying matter can be turned into CO2. So many feel that low water movement in a NPT is good as CO2 levels can get above ambient levels(has been tested in natural bodies of water). In a regular substrate tank, many feel that good surface agitation is good and will try to keep the co2 levels near ambient.


There may very well be a point which is too long for the "siesta", where plants will not adapt very well,so that will have to be considered.

So in a DIY or non CO2 injected tank, my opinion is that for the "siesta" to be used to the most benefit, the 1st lighting period should be even for a DIY CO2 tank, the period in between will be found by finding out how long it takes when the lights go out for the CO2 levels to build back up. If it takes to long to build back up, then the last lighting period should be shorter then the 1st.


If its non CO2 injected tank, then the CO2 will prob build up slower when the lights are off depending on the method. So you may need a longer "siesta" to give time for the CO2 levels to rise, it may also not have enough tie to rise to what it 1st was, In this case its prob best to have the last lighting period shorter than the 1st.




Please add your $.02

My only thought on this is that no one has yet presented any data that demonstrate a benefit to the split photoperiod, as far as I have seen. The one benefit seems to be allowing people who are away from home during the day to enjoy their aquarium both in the early morning before leaving, and in the late afternoon or night after returning home. If that benefit isn't accompanied by problems from using the split photoperiod then I see that as a good way to run the aquarium. And, I don't recall anyone demonstrating that there are problems that result.

Thanks Hoppy!

I guess instead of using my perfect test mentioned above, the straight test would be just testing a DIY co2 tank or non injected tank and comparing growth. From this test we could assure if it has any benefits or not, just cannot pinpoint the root cause of the gains.


Thats why I was asking. If people have proven that a siesta works equally well in a high flow/steady CO2 tank compared to a straight light period, this is the question! This would answer the root question.

Then if straight lighting period had the same growth as the split period, we could assume that there would be added benefits for a DIY co2 injected tank or a non injected tank including NPT. These benefits would be the ones mentioned above, mainly CO2 levels not dropping as much and given time to raise.


Do you agree that cutting the lights for a siesta in the middle of the photo period will give time for the CO2 levels to rise?
Seems logical to me at least in a DIY CO2 tank or a NPT with little water flow and higher then ambient CO2 levels.


I'm just not sure about a non injected tank that relies on CO2 from the air/water exchange. I guess if the CO2 in the water is replenished as fast as plants can consume it, it doesnt matter.

I would definitely defer to Diana Walstad on the effect of a split photoperiod on an "el natural" tank. And, I have no opinion at all about the effect on any tanks, other that what I stated.

To do any cause of effective control test with algae, you must first induce algae growth and then do any treatment.

This way you have the same starting point and relative place to compare treatments and rep's.

This is very basic stuff, but few hobbyists seem to have any idea about how to go about it, since most just want to the algae to go away and really do not care about why it is there in the first place.

They might even care, however, not enough to induce the algae and then research treatment methods.

And that is really the bottom line why so many myths, issues and really lack of knowledge about algae.

As far as I know, myself and a few others are the only people that have looked at specific cause. I've never met a single hobbyists that has done any real test for inducement.

Think about it, if you know what starts an algae bloom, then you know the cause specifically. Then you can prevent it and prevent new growth occurrence.
This concept is lost on many. Some would rather claim PO4 causes algae and carry on like wind bags without doing anything to answer the real question.

Yack yack and no work, no test, they just are "smart". I'm not so smart and know it, so I have to use methods to make sure what I do and what I conclude is well founded and is reasonable.

That's why I start at the same place when comparing treatments to a specific species of algae. Not doing so, not acknowledging this etc....you make yourself look foolish to anyone that's done any testing with algae. The Do Nothings really have no opus to say anything about algae cause.

I do not make good friends with Do nothings, but that's tough.
That's their problem. Show me a test, show me how the method/test results you use supports the question you ask.

Then do the test and repeat it a few times, under a few different conditions, treatments etc. Let us know you gave things some consideration and the problems you found a long the way.

Speculation is fun, but does not answer the question.
IME and IMO, siesta does little and only reduces the CO2 demand for a bit to help the plants, thus is a indirect effect, one that does not address/answer the root cause: why you have algae in the first place.

Then if you address the root cause, then go back and test the siesta, now we see if has no effect. We induce the algae again, and it still does not...........

So the results are fairly clear to me.
The rest of the folks, and a horde of me too's hop on board and act like a mob.........

I've seen this 100X at least over the years.
20-30x on this one subject
And still the myth is continued.
Does not matter what results or what I say, the myth will keep going.


Regards,
Tom Barr

I never mentioned using a siesta for algae!!! Strictly based on CO2 levels in a non optimal CO2 tank.


OK sorry for all the questions and wasting time. I should have done more research before asking or assuming things.

I found a great thread which Tom gives real answers.

Aquatic Gardeners Association :: View topic - Siesta w.r.t. Lights

Basically says what I was looking for in terms of CO2. So a "siesta" could be useful if you have a low supply of DIY co2 that falls way down by the end of the lighting period.

If NPT tanks hold higher than ambient CO2 levels, I could see that helping them also.

In this thread he says similar things, but its more directed towards algae
"Siesta" for lighting to combat algae? [Archive] - Aquaria Central


Now that being said, others with pressurized CO2 I have found seem to feel a straight photo period is better then the split period(having the CO2 on the whole time).

So that is basically what I was asking. Basically what I got from my research is that a "siesta" is not optimal if you have optimal conditions(co2), similar to how many like a "noon burst" which would be the opposite.

It is yet to be seen if there would be any affect on a non CO2/non NPT tank. I doubt it and dont plan on testing, I'm too worried about burning out my expensive T8 bulbs faster then usual, lol. Just looking for info and I found what I was looking for.

No, I should have read that you had no algae question in there.
However, I've yet to met anyone that asks about siesta without the real issue being poor plant growth and most commonly, algae.

So they go hand in hand.


You got it.

Folks need to be careful when they think one things causes something directly.
Was it the siesta?
Or was it the poor CO2 system?
Valid questions, and some proponents of the siesta do not like such questions.

So you set up a simple test to see.
Then you know it's likely the CO2 and you know it's certainly not the siesta.

And unlike the siesta, the test results show why algae or poor plant growth observations are in many tanks, with and without siesta.

We can get poor plant growth and algae easily by manipulating CO2 and even more so as we increase light in all cases.

Regards,
Tom Barr