Questions on photo period

[tiger15]

I have been browsing this forum for a while and am impressed by many knowledgeable posters. I finally registered today and post my first questions on photo period. I am aware the subject has been discussed many times before but didn't quite answer my specific questions.

Based on my search, there is a consensus to limit the photo period to 8 hours in CO2 tanks. The explanation is that plants shut down photosynthesis in about 8 hours as evident by some stem plants closing up. So any longer lighting will be wasted or worse, trigger algae.

Question 1: Many aquarium plants are tropical. The average day light hour in the tropic is 12 hour. So in nature, photo period longer than 8 hour is normal, right?

Question 2: Certain stem plants response is not an evidence that all plants respond the same. I keep mostly slow growing Java fern, Anubias, Crypts and Buce and they don't necessarily shut down as stems, but I have no way of telling because they don't open and close up like stems. I have never observed closing and opening of my easy stems: Rotala rotundifolia and Luwigia repens. So why is 8 hour photo period universally accepted as optimum for CO2 tanks?

Question 3: If indeed plants shut down after 8 hours continuous lighting, wouldn't splitting a long photo period into two promotes more growth? Walstad method advocates for a siesta period to allow recovery of CO2 which obviously doesn't apply to CO2 tanks. But wouldn't a siesta period that splits up a long photo period bypass natural shut down and fool the plant into double growth?

I love to be able to increase growth by increasing the lighting period and/or splitting a long lighting period rather than by increasing the light intensity. Longer lighting period gives me enjoyment of longer viewing time and avoids intense light and thereby less wriggle room for other variables.

I love to hear your opinion or experience on this.

 

[foxfish]

Hi and welcome to the forum.
Some folk do indeed use longer lighting periods, 6-8 hours a day is recommend to get beginners on the right track without causing too much algae.
However if you are confident that your tank is under control then you can increase the lighting period a little at a time.
You have to bare in mind though, some folk complain about high maintenance & super fast growth with only 6-8 hours of light, so perhaps you have not quite got your C02 dialled in too its optimum potential.

 

[ian_m]

The average day light hour in the tropic is 12 hour. So in nature, photo period longer than 8 hour is normal, right?

Because in nature the photo period is not full sunlight for 12 hours. It starts in the morning at zero light, maybe max at midday and zero light at sunset. If you have super duper aquarium light fixture that allows timed dimming, you may be able to reproduce this. Most of us have simple on off lights so 8 hours "on average" is probably far more light energy than plants would receive in the real world over 12 hours.

Splitting photo period is one of those aquarium myths that reappears all the time. Plants use energy and take a while to get photo synthesising (maybe upto 3 hours) so two 4hour lighting periods does not necessarily result in better plant health than one 8 hour period. Most people here use just one lighting period and control lighting intensity and lighting period to keep healthy plants and algae free tanks.

Stop "wasting worries" about lighting period and spend more time on getting CO2 levels and distribution right. This is the thing 99% of plant keepers with tank issues are missing, they worry about lighting periods, fertiliser dosing, colour of their filter tubes, my mate does such and such, my tap water contains things, my underwear in yellow etc etc when in fact all along their CO2 implementation is crap.

 

[Kezzab]

I have had the wrong underwear issue, don't discount it so readily.

 

[Tim Harrison]

Hello Tiger and welcome.

What we aim to do in our aquariums is try and grow healthy plants free from algae by providing optimal conditions, conditions plants won't necessarily get in nature, like Ian mentions above.
6-8hrs of light is sufficient to allow us to do that. But like foxfish mentions many folk use longer photoperiods, it just gets harder to keep them algae free.

Most submerged macrophytes are considered shade plants since they have several adaptations that make them very efficient photosynthesisers at low light levels.
So perhaps more important than light duration is light intensity. Most folk expose their plants to way too much light, and this is where most of the problems start.
The higher the light intensity the more difficult to optimise flow, fertz and CO2 distribution; less wriggle room for mistakes and greater risk of algae.

As you've pointed out different species of plants have different physiological responses to different stimuli. Species such as Anubias and Java fern are adapted to very low light forest conditions and have a very low light compensation point; for instance, they have no need to close up since too much light is never going to be a problem in their natural habitat. They are however, by nature, slow growing and therefore very susceptible to algae; if the light is too intense they soon become covered.

With regards a siesta period, I don't know of any peer reviewed information that suggests this actually works, even in a low-energy non-CO2 tank. However, if a siesta period is more convenient for you in terms of viewing then I doubt it'll hurt. Check this link out https://www.ukaps.org/forum/threads/lighting-photoperiod-rest.51380/#post-504767

 

[tiger15]

Splitting photo period is one of those aquarium myths that reappears all the time. Plants use energy and take a while to get photo synthesising (maybe upto 3 hours) so two 4hour lighting periods does not necessarily result in better plant health than one 8 hour period. Most people here use just one lighting period and control lighting intensity and lighting period to keep healthy plants and algae free tanks.
.

If it takes up to 3 hours to get going with photosynthesis, what’s the benefit of starting co2 1 to 2 hours before light on. The plants won’t be ready to utilize co2 in full gear right away, so why not synchronize co2 and light on at the same starting time.

I don’t mean two 4 hour lighting period, more like 5 or 6 to give a total of 10 to 12 hour total. That way it can bypass the natural 8 hour shut down and give plants extra growing time.

 

[ian_m]

If it takes up to 3 hours to get going with photosynthesis, what’s the benefit of starting co2 1 to 2 hours before light on. The plants won’t be ready to utilize co2 in full gear right away, so why not synchronize co2 and light on at the same starting time.

The CO2 two hours before lights on is the required time to infuse CO2 to 30ppm level in the water, so that when lights come on the CO2 level is steady. Varying CO2 levels during light period due to poor CO2 management is the start of poor plant health and algae making an appearance.

See here for the maths on CO2 levels vs time. For a typical tank 2 hours on before light appears to be a good start.
https://www.ukaps.org/forum/threads/co2-concentration-versus-time-the-maths.51423/

See Zeus's system for how to achieve 30ppm in much shorter time. (dual injectors bit...).
https://www.ukaps.org/forum/threads/olympus-is-calling.43046/

I don’t mean two 4 hour lighting period, more like 5 or 6 to give a total of 10 to 12 hour total. That way it can bypass the natural 8 hour shut down and give plants extra growing time.

As stated by Tim there is no information that implies this works. If you try let us know.

 

[Edvet]

The split period originates from "walstad method" tanks. The idea was the rest period in between functions as a time to let CO2 levels get higher again, so plants benefited from higher levels of CO2 as compared to one period. In reality it hasn't shown to work in measurable ways.
The low energy "walstad" tank will have slow growing plants, no need to force higher growth rates.

 

[tiger15]

So perhaps more important than light duration is light intensity. Most folk expose their plants to way too much light, and this is where most of the problems start.
The higher the light intensity the more difficult to optimise flow, fertz and CO2 distribution; less wriggle room for mistakes and greater risk of algae.

With regards a siesta period, I don't know of any peer reviewed information that suggests this actually works, even in a low-energy non-CO2 tank

This is exactly why I want to play around with the light duration rather than the light intensity. I have low to medium light, around 50 par at the substrate, so too high light intensity is never my issue, but then I am limiting to growing only low light plants. Even with co2, they still grow too slowly to me. I am exploring if increasing light duration can induce faster growth without inducing but out pacing algae.

I read the link on siester period and am aware that there is no proof that siester can reduce algae competition, but what about higher growth rate due to recovery of co2 in non co2 tanks?

 

[Zeus.]

Clive (our CO2 Guru) does advise a lower light intensity for the fist 30mins, this is to allow a 'wake up' time for the plants as they are not really ready for full light intensity when the lights first come on so cant photosynthesis at their full potentail thats a little time to reach it. Which is what happens in the real world OFC. so too much light when lights first come on gives algea the edge. Max [CO2] at lights on is important too then stable for rest of photoperiod.

My photoperiod is 6.5hours with peaks and drops thoughtout the period. some lights going up to 60% intensity whilst others only reach 30%. the difference is to match the depth of the leaves varing from just below the surface to 50cm deep with my carpet. it is tricky to get it right and still working on getting mine right and planted it over a year ago

 

[Tim Harrison]

I am exploring if increasing light duration can induce faster growth without inducing but out pacing algae

Depends on the plant species, and the plant morphology you hope to achieve, e.g. low compact growth.
Some species won't thrive on too low an intensity or grow how you'd like them too, no matter how long the duration, although high CO2 conc will help to a degree.

 

[zozo]

In discussion like this i just can't help to mention.. If you live in temporate regions with summers that at it's height has 18 hour daylight. Than find a succesfull pond owner with a clean algae free pond.. Take a look at it and ask yourself "How is that possible?" That would be 18 hour daylight at an intensity any invented lamp can not match.. And it works, not for all but it is absolutely possible.

Indoor in a little invironment we certainly have some ristrictive differences to take into account.. But it aint the photo periode..

 

[Edvet]

ummers that at it's height has 18 hour daylight

yeah but it starts with a few hours overcast and gradually builds up, and all the plants that can't handle that are gone.And look at all the algae products for ponds in the gardencentres

 

[tiger15]

Depends on the plant species, and the plant morphology you hope to achieve, e.g. low compact growth.
Some species won't thrive on too low an intensity or grow how you'd like them too, no matter how long the duration, although high CO2 conc will help to a degree.

I understand photo compensation level below which plants won't grow regardless of light duration. So substituting longer light duration for lower light intensity doesn't work with plants that don't receive enough light above PCL.

I have low light plants and all receive light above PCLs, as evident by growth notwithstanding slow to very slow. My tank is 95% algae free except for light bba on the edges of slow growing Anubias and Buce leaves. The faster Java fern and Crypts are fine. I know increasing light intensity will likely hurt than help, but wonder if increasing photo period or having long split periods will help or hurt.

 

[zozo]

yeah but it starts with a few hours overcast and gradually builds up, and all the plants that can't handle that are gone.And look at all the algae products for ponds in the gardencentres

I personaly experience it different.. My tub gets full blast from 9 in the morning with the sun already peaking over the roof till the night fall. And the light at 9 o clock in the morning is brighter than any bulb invented. I also exprience this with my low tech that stands in door under the skylight. On a day without clouds the tank is brighter lit from the day light at 9 in the morning than from the bulbs hanging above it. Can't even see the bulbs light reflection on the wall anymore and don't see the difference when i switch them off. And thats what i do all summer long, than it's a naturaly daylight lit indoor aqaurium. for the full periode i might add, can't switch off nor dim the sun. And i invite you to come and have a look at the non exploding algae.

And i do not know how many of you guys have been in teh tropics.. But the 12 hour days at the equator ar freaking fast from dawn to full blast and from full blast to dusk. It's minutes.. A bit excaggerated but in my experience compaired it was like POING there is a sun in the morning and PLOP the sun fals in the ocian at night in a blink of an eye.

 

[tiger15]

yeah but it starts with a few hours overcast and gradually builds up, and all the plants that can't handle that are gone.And look at all the algae products for ponds in the gardencentres

But pond plants don't get bba, but all other algae. All other algae don't bother tank plants persistently and can easily be controlled, except for evil BBA.

 

[zozo]

But pond plants don't get bba

Indeed never had it in the garden, even throw completely BBA infested indoor plants into the garden tub and they come out clean. Till now the only algae i experiences outdoor is diatomes, aufwugs and Cladophora.. And clado only in the fishless setups.. Goldfish seem to eat it for breakfast.

BBA likely is an from the LFS introduced tropical algae sp. Can't coop with the lower temps. I dunno.. Best guess..

 

[Angus]

my underwear in yellow etc etc

When i put on my tighties instead of my boxers it definitely results in some BBA around the edges....

 

[Edvet]

All the plants in nature grow where they thrive, if not they disappear.

 

[Tim Harrison]

So I wonder if longer photo period or split photo periods will help or hurt.

Give it a go, change one variable at a time; either increase photoperiod or use a siesta period and see if it makes any difference.

I doubt a siesta period will make much difference to growth or algal inhibition, but like I mentioned above, use it if it suits your viewing timetable better.
Extending the photoperiod will probably increase the growth rate of your crypts and ferns, but BBA is a sign of unstable CO2 so your anubias will probably suffer.

You'll probably get better results all round by increasing surface agitation and improving atmospheric gas exchange, at least CO2 conc is more likely to remain stable. https://www.ukaps.org/forum/threads/maxing-co2-in-low-techs.29856/page-3#post-330177