# When to have lights on



## GraemeVW (21 Aug 2022)

Maybe an odd question, but im sure i read somewhere that plants will start photosynthesising as soon as there is daylight in the room.
I also read they will only photosynthesis for 12 hours.

If I have my lights on mainly in the evening then the plants have already given up for alot of the high light period.

Does this matter?
Is it even true?


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## erwin123 (21 Aug 2022)

with certain plants it is easy to tell - eg: Pantanal, because they will start 'closing up'  to tell you they are done for the day.  So maybe having one or two of those types of plants in your tank may be a good indicator.


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## GraemeVW (21 Aug 2022)

erwin123 said:


> with certain plants it is easy to tell - eg: Pantanal, because they will start 'closing up'  to tell you they are done for the day.  So maybe having one or two of those types of plants in your tank may be a good indicator.


I did write more, but decided to keep my post shorter.

Maybe 1/3rd of my cabomba closes up around 7 ish, when my lights are still on full. They are all fully open way before my lights come on.

I guess, if the plants aren't using the light, then all I'm doing is growing algae.

Even though I like having it lit in the evening, maybe I'd be better off moving the photo period earlier. 
Trying to gauge the truth of the matter to see if it matters much.

My main light is programmable so I could still have low light in the evening.


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## JoshP12 (21 Aug 2022)

GraemeVW said:


> Maybe an odd question, but im sure i read somewhere that plants will start photosynthesising as soon as there is daylight in the room.


Yep.


GraemeVW said:


> I also read they will only photosynthesis for 12 hours.


They photosynthesize as long as light hits them. They may adapt to long photoperiods by closing up early as you observe but they haven’t stopped photosynthesizing, they are just moderating how much light drives them.


If I have my lights on mainly in the evening then the plants have already given up for alot of the high light period.


GraemeVW said:


> Does this matter?
> Is it even true?



I mean, some of them look really pretty when they are closed up. You could cut your lights early or reduce light that gets at them before their photoperiod … you can shift their open and closing pattern by adjusting your photoperiod and moderating the amount of light that gets into the tank.

I take it you don’t have an algae issue since your plants are behaving this way … I wouldn’t worry unless you want them to close as you dim your lights … it does look neat.


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## GraemeVW (22 Aug 2022)

No algae issue at the moment but the tank is only a month old.


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## dw1305 (22 Aug 2022)

Hi all,


GraemeVW said:


> If I have my lights on mainly in the evening then the plants have already given up for alot of the high light period.


The tanks at home come on about 07:30, so I get a <"quick look before work">, mornings <"aren't a great time for me">, so hopefully I go to work a little bit happier. 

Then they have a couple of hours of about midday and then come back on until about 20:30 ish. They are in the kitchen which gets a lot of ambient light, and if I'm home I tend to over ride the time switch so the lights are on all day.

I like a <"12 hour day">, but I'm not too bothered whether that is 10 or 14 hours.

The tanks in the lab. come on at 07:00 and go off at 19:00, without a siesta. This is so I'm occasionally about when the <"lights should be off">.

cheers Darrel


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## GraemeVW (22 Aug 2022)

I noticed this morning the cabomba was open by 7.30 with ambient light.

I might move the main light period to match what the plants are showing and just have low light on the evening. It looks live with just a low, central light.


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## oreo57 (16 Sep 2022)

Plants can tell the time using sugars
					

A new study has found that plants adjust their daily circadian rhythm to the cycle of day and night by measuring the amount of sugars in their cells.



					www.sciencedaily.com
				





> For example, circadian rhythms control the time when plants grow, when their flowers open and release scent, and allow plants to carefully use energy reserves so they do not starve in the night.
> 
> Circadian rhythms also help plants to detect changes in the seasons, which is crucial to ensure our crops mature in the correct season.


Theoretically one should be able to "reset" them to any time period you choose..  again theoretically..


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## _Maq_ (16 Sep 2022)

JoshP12 said:


> They photosynthesize as long as light hits them.


@oreo57 's post may explain why your experience differs from mine. If circadian rhythms are controlled by _sugars created_ during photosynthesis, then your plants may create sugars for very long period, because they have unlimited access to CO2. While in my low-tech tanks CO2 is (presumably) largely depleted in late afternoon, so the plants have no choice but 'to go to bed'. What do you think?


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## JoshP12 (16 Sep 2022)

_Maq_ said:


> @oreo57 's post may explain why your experience differs from mine. If circadian rhythms are controlled by _sugars created_ during photosynthesis, then your plants may create sugars for very long period, because they have unlimited access to CO2. While in my low-tech tanks CO2 is (presumably) largely depleted in late afternoon, so the plants have no choice but 'to go to bed'. What do you think?


I like it.

I think there is a difference between growth and photosynthesis though. 

If light activated the electron transport chain, the plant will photosynthesize and start making sugar. 

Sugar availability will dictate growth. 

Certainly, the plant moderates light intake by changing its “shape” … closing up for example to mitigate how much light hits the actual leaves … mine have done this before.


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## oreo57 (16 Sep 2022)

Dialing
PLANT CIRCADIAN CLOCK​
to 11..





						Circadian Rhythms in Plants
					

A new type of review journal, featuring comprehensive collections of expert review articles on important topics in the molecular life sciences



					cshperspectives.cshlp.org


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## tiger15 (17 Sep 2022)

Photosynthesis will not be activated  by ambient light if it does not exceed the plant  light compensation point.  Indoor ambient light is typically below LCP and this is why artificial light is needed to grow aquarium plants.  So aquarium plant circadian clock is artificial,  not measurable by ambient light, but by man made photo period.

The question is whether the artificial circadian clock  is cumulative, that is, if there is a siesta period, will the split time be added up.

Closing of Cabomba like plant may indicate the plant has stopped photosynthesis, but opening may not necessarily indicate active photosynthesis, just readiness to begin when the artificial light is on.   

A better way to measure photosynthesis is streaming if the plant is under high light.  My window sill planted bowl begins streaming when sunlight hit, and slows down or stops  instantly when cloud passes by.


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## oreo57 (17 Sep 2022)

tiger15 said:


> Photosynthesis will not be activated  by ambient light if it does not exceed the plant  light compensation point.  Indoor ambient light is typically below LCP and this is why artificial light is needed to grow aquarium plants.  So aquarium plant circadian clock is artificial,  not measurable by ambient light, but by man made photo period.


No, it doesn't work like that.. Below the light compensation point respiration exceeds photosynthesis.
It is not the point of  no photosynthesis.
Anyways the wonderful "complication"








						How do plants rest photosynthetic activity at night?
					

Scientists at Tokyo Institute of Technology have identified two proteins that allow plants to respond to changes in surrounding light conditions and thereby make photosynthesis more efficient.



					www.eurekalert.org
				





> TrxL2/2CP do work in light as well, but are overshadowed by the normal activation machinery in plants and only take center stage in the absence of light. Interestingly, this cascade does not seem to affect photosynthesis itself, as mutant plants without 2CP behave normally in light; however, the 'switching off' mechanism is significantly less efficient in these mutant plants than in wild-type plants. Moreover, the fact that this process is less efficient, rather than absent altogether, suggests that other, as yet unknown, proteins serve similar functions in plants. These researchers thus shed light on how plants reserve the activity of photosynthetic proteins for when it's actually useful.





			https://www.science.org/doi/10.1126/sciadv.abi8307
		



Respiration occurs 24/7..


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## _Maq_ (17 Sep 2022)

@oreo57 , thank you very much for an enlightenment.


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## oreo57 (17 Sep 2022)

_Maq_ said:


> @oreo57 , thank you very much for an enlightenment.


Not sure it" helps" anything... 
but it is interesting.


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## tiger15 (17 Sep 2022)

oreo57 said:


> No, it doesn't work like that.. Below the light compensation point respiration exceeds photosynthesis.
> It is not the point of  no photosynthesis.
> Anyways the wonderful "complication"
> 
> ...


No net photosynthesis is technically the same as no photosynthesis, no sugar accumulation, and no net oxygen production.  The OP thread asked when is the best photo period for optimal photosynthesis.  If ambient light starts the circadian clock, then any night time photo period is a waste.   This is not supported in practice as majority aquarists turn on light in the evening to view tanks, and their plants should be stunt.   I think Dennis Wong said that the first 4 hours of photo period is most productive for photosynthesis,  which disminishes gradually thereafter, and any additional lighting beyond 12 hour is a waste.  So he recommends that CO2 should be front loaded couple hours before light on.  I can’t find  his exact citation, perhaps someone can help.


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## _Maq_ (17 Sep 2022)

tiger15 said:


> I think Dennis Wong said that the first 4 hours of photo period is most productive for photosynthesis, which disminishes gradually thereafter, and any additional lighting beyond 12 hour is a waste. So he recommends that CO2 should be front loaded couple hours before light on. I can’t find his exact citation, perhaps someone can help.


It's commented, among others, in Wetzel's Limnology. It is suggested that it has something to do with photorespiration which increases with O2 concentration near photosynthesizing cells.
In natural waters and in low-tech tanks another factor is even more important: a decrease in CO2 concentration. CO2 is often depleted around noon in natural waters. I think the same happens in low-tech tanks, so plants quit photosynthesis even if lights are still on. That's in line with my observation.
So it seems that CO2 injection makes all the difference.


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## oreo57 (17 Sep 2022)

> *>>>Photorespiration*





> (also known as the *oxidative photosynthetic carbon cycle* or *C2 cycle*) refers to a process in plant metabolism where the enzyme RuBisCO oxygenates RuBP, wasting some of the energy produced by photosynthesis. The desired reaction is the addition of carbon dioxide to RuBP (carboxylation), a key step in the Calvin–Benson cycle, but approximately 25% of reactions by RuBisCO instead add oxygen to RuBP (oxygenation), creating a product that cannot be used within the Calvin–Benson cycle. This process lowers the efficiency of photosynthesis, potentially lowering photosynthetic output by 25% in C3 plants.[1]<<<


Mysteries..








						A short history of RubisCO: The rise and fall (?) of Nature’s predominant CO2 fixing enzyme
					

Ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) is arguably one of the most abundant proteins in the biosphere and a key enzyme in the global carbon cycle. Although RubisCO has been intensively studied, its evolutionary origins and rise as Nature’s ...




					www.ncbi.nlm.nih.gov


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## tiger15 (18 Sep 2022)

_Maq_ said:


> It's commented, among others, in Wetzel's Limnology. It is suggested that it has something to do with photorespiration which increases with O2 concentration near photosynthesizing cells.
> In natural waters and in low-tech tanks another factor is even more important: a decrease in CO2 concentration. CO2 is often depleted around noon in natural waters. I think the same happens in low-tech tanks, so plants quit photosynthesis even if lights are still on. That's in line with my observation.
> So it seems that CO2 injection makes all the difference.


The photosynthetic depletion of CO2 in lakes has been documented in many limnology studies, and cited in Walstad book in support of a siesta period in low tech tanks.   I can validate it in my window sill planted bowl where pH fluctuates between 7.2 to 8.8 pre and post sunlight period, and with kH 3, the calculated CO2 fluctuates between 3.6 to 0.1 ppm respectively.   Growth is very slow though despite vigorous streaming at peak sunlight due to CO2 limitation.   Siesta period is not believed to have any benefit in high tech tank, but I provide it anyway to fit my viewing schedule.   I’ve never observed closing of  stems after mid day siesta in my high tech tank, only in the morning when light turns on.


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## _Maq_ (19 Sep 2022)

Again and again, I find it amazing how smart plants are. Regulating diurnal rhythms by sugar production? But of course, that's the end-product, that's the point of it all. Both carbon dioxide and light are irrelevant if the other is missing - there's no point in activating photosynthesizing enzymes. How smart...


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## Yugang (30 Sep 2022)

dw1305 said:


> I like a <"12 hour day">, but I'm not too bothered whether that is 10 or 14 hours.


I'm now trying to understand the lower limits. How about 6 hours?

My tank has been on a 6 hours light on for the last year, but recently I have been struggling to get it back into it's best shape. I was blaming the hot HK summer (still today my tank is at 30-31 degrees C), but I have started to doubt if that's the real issue. Perhaps my tank photoperiod has been my blind spot, I double checked many other parameters, so I increased it to see what happens.

I checked a couple of journals, 8-10 hours seems to be the average. Some reported 6 hours (@KirstyF ?). My question is whether 6 hours photoperiod is still acceptable for a high tech tank, or does it make life challenging for some plants?

Note: the 6 hours mentioned is full lights on, in the evening I dim the light for a more relaxed ambiance


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## MichaelJ (30 Sep 2022)

dw1305 said:


> I like a <"12 hour day">, but I'm not too bothered whether that is 10 or 14 hours.


I am a believer in long photoperiods as well.  Most of our plants comes from around the equator where they get about 12 hours of light.  My light ramps up around 11:30am (30 minutes ramp) and ramps down at midnight.  My tanks only get a tiny amount of ambient light in the room where they are located.  If the long photoperiods wouldn't work, I would have a hard time enjoying my tanks. I like to pop in and enjoy the tanks throughout the day and the evening. 

Cheers,
Michael


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## KirstyF (30 Sep 2022)

Yugang said:


> I'm now trying to understand the lower limits. How about 6 hours?
> 
> My tank has been on a 6 hours light on for the last year, but recently I have been struggling to get it back into it's best shape. I was blaming the hot HK summer (still today my tank is at 30-31 degrees C), but I have started to doubt if that's the real issue. Perhaps my tank photoperiod has been my blind spot, I double checked many other parameters, so I increased it to see what happens.
> 
> ...



The 6hrs was for a period of time at start up to help the tank stabilise but was then slowly increased and is now 8.5hrs. 

I chose to increase in 30min increments over a number of weeks (and extend Co2 period accordingly) so that I could assess impact as I went along.

I would certainly say that some of my stem plants showed stronger growth as a result but I guess it depends on what you mean by ‘best shape’, what you are growing and/or what issues you are noting.

I also have a 30min ramp up/ramp down time in addition to the above (I believe the fish are happier with that) but don’t run an extended ‘low light’ period. I feel that this in itself may cause issues if the light is of little benefit to plants but still enough to be beneficial to algae, although again I guess that may depend on how low the light is when dimmed. 

IMO, increasing ur photoperiod is unlikely to do any harm and ur plants may well appreciate it, so long as you observe how the tank/plants respond, they will let you know.


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## dw1305 (30 Sep 2022)

Hi all, 


Yugang said:


> How about 6 hours?


I don't really see how 18 hours of darkness can be optimal for any plant. 


MichaelJ said:


> Most of our plants comes from around the equator where they get about 12 hours of light.


That would really be <"where I'm coming from">.

cheers Darrel


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## Yugang (1 Oct 2022)

KirstyF said:


> I would certainly say that some of my stem plants showed stronger growth as a result but I guess it depends on what you mean by ‘best shape’, what you are growing and/or what issues you are noting.


I feel a bit silly now, because it seems rather obvious that 6 hours is unnecessarily short. 
I had adjusted lighting period down (6 hours, plus a couple of hours progressively dimmed in the evening), as at the time I wanted to 'slow down' my tank and preserve it in it's happy state with less CO2 consumption and less pruning. Initially, at least for a couple of months this worked well, not sure why, and why that changed later, and I then mistakenly assumed this was a good basis and lighting period became my blind spot (pun intended). 

Now a couple of days 9 hours full lights on, and my tank is making fun of me with all my sophisticated scenarios I had dreamed up why my rotalas, wallichi, and even anubias seemed not happy anymore 😥 Sometimes we miss the obvious...

Thanks @MichaelJ , @KirstyF and @dw1305 , your replies were very helpful.


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## Hufsa (3 Oct 2022)

Yugang said:


> 6 hours is unnecessarily short
> ...
> Now a couple of days 9 hours full lights on, and my tank is making fun of me


6 always seemed really short to me, my tank has been chilling at 8 for a while now and I almost think I have just gotten used to the short-ish photoperiod. 
I have always been drawn towards the equator sun / 12 hours idea/concept/something, just not sure how to implement it well.
Yesterday I increased to 10 hours, and hope the tank takes it in its stride  Would love to end up at 12 eventually.

Can you describe what you have observed after increasing?


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## tiger15 (3 Oct 2022)

6 hour intense lighting is fine.  I have seen one poster whose meticulous high tech nature tanks get only 6 hour photo period and he claimed it is a trick to keep  algae out of healthy plants.  Dennis Wong cited that photosynthesis is most intense in the first 4 hours and diminishes thereafter, so 6 hours is more than enough.  Trying to replicate 12 hour natural cycle in nature tanks is unnecessary as nature tanks are unnatural to begin with.   A number of  popular aquatic plants are not from the tropic, such as Ludwigia and Sagittaria species from North America, and many stream bank tropicals don't get 12 hour sun due to moving tree canopy shade.   However, 6 hour viewing time is too short for my enjoyment,  so my lighting schedule is 4.5 hour in the morning and 4.5 hour in the evening.   If Dennis Wong's claim is true, then I am providing daily double optimizing photo periods, and siesta period is good for both low and high tech tanks.


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## MichaelJ (3 Oct 2022)

tiger15 said:


> However, 6 hour viewing time is too short for my enjoyment, so my lighting schedule is 4.5 hour in the morning and 4.5 hour in the evening. If Dennis Wong's claim is true, then I am providing daily double optimizing photo periods, and siesta period is good for both low and high tech tanks.


Viewing time is my greatest concern as well. My viewing is fairly sporadic throughout the day, so the siesta period probably wouldn't work, but I do like the idea and potential benefits (I'll have to read up on what Mr. Wong is saying).   As said, 6 hours just seems like an extremely short and _unnatural_ photoperiod.  Also,  one need to consider a proper balance between photoperiod and light intensity. I don't think I could pull off the +12 hours in both my low-tech tanks if I had  intense light.



tiger15 said:


> A number of popular aquatic plants are not from the tropic, such as Ludwigia and Sagittaria species from North America


True. Some popular species (some introduced) are widely found outside the tropical zone such as the lower part of North America (where daylight varies between 10.5h to 13.5h depending on the season).

Cheers,
Michael


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## tiger15 (3 Oct 2022)

6 hours seem short because the average photo period is between 8 to 10 hours.  But if it is 6 hour full intensity light with no CO2 dial down, it's not that short.    Dennis Wong suggests turning on CO2 1 to 2 hour before light on and off CO2 1 to 2 hour before light off, but for photo period 6 hour and under, he suggests no CO2 dial down.

Siesta works best for me for viewing as I feed  my fish first thing in the morning before sun rise, and again in the evening after sun set when I am home all night.  I can still see my fish during the siesta period under low ambient light.


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## Yugang (4 Oct 2022)

Hufsa said:


> Can you describe what you have observed after increasing?


It is a bit early to celebrate, mysteriously several plants that used to do very well have been stuggling recently. I checked my log of all changes, and have a pretty long list of (mostly unlikely) root causes (including high temperature, frontloading macros, dosing CaCl, stopped using commercial remineralisation, stopped using crushed eggshell, change of commercial dechloritator, ...).

None of my intended corrrections really had a significant impact, but after increasing the photo period to 9 hours I see a lot more pearling, even early in the photoperiod. I am waiting for some convincing evidence that struggling plants recover.



Yugang said:


> Note: the 6 hours mentioned is full lights on, in the evening I dim the light for a more relaxed ambiance


I was not exactly on 6 hours, because the start of my evening ramp down would still be close to 100% and I find it hard to quantify that to a full light equivalent. Perhaps nett 7 hours would be more fair.
Just a few days ago my Juwel HeliaLux controller broke down again (second time in three years ), I put the lights on a simple timer and have now a more accurate 9 hours full light + 3 hours half light (and the spectrum equivalent of a cheap LED light).


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## JoshP12 (4 Oct 2022)

I think this in part what I was eluding to here
Post in thread 'A reflection - putting it all into one scape'
A reflection - putting it all into one scape

Perhaps since the functionality of rubisco increases with pH (and decreases with lower pH), it may need longer periods of light in co2 is supplemented at large rates (low ph) for the entire photoperiod. However, if we ease off/cut off the gas a few hours before the end, perhaps allowing the pH to swing up will allow the stored co2 in the plant to be use up via a more effective rubisco?

Rubisco only functions in the light and if we provide low pH the whole time, it won’t function at its “ finest” and maybe the plant won’t be able to make enough sugar to keep up with metabolism?

It would make a whole lot of sense (lol maybe?) @Yugang  if they’re pearling more with longer photoperiods since there is more time for them to use RubisCo and make more sugar —-  I reckon the increased pearling didn’t happen day 1, but a few days or even a week after? It’s possible that the extra sugar that they made gave them a “boost”, then they decided that they can really do something with this much light and then bam start going full on?!

Now that sounds crazy - just saying. Did they pearl instantly?

Edit: getting their fill of co2 doesn’t necessarily mean getting their fill of sugar - does it?


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## KirstyF (4 Oct 2022)

Just curious! Can I ask what is the RubisCo relationship with Ph if anyone knows. I have read somewhere that it pretty much ceases function at a ph lower than 6 or higher than 10 but I’m not sure on exactly where the curve lies (or even if that is accurate) 

If the above supposition is correct then comparing a tank that sits at 6.6ph after a full 1ph drop due to Co2, and one that starts at 6.6ph before Co2 kicks in you would have very different results. 

The high Ph tank would effectively sit in a sweeter spot throughout its entire photoperiod than a low Ph tank could achieve, even if fully de-gassed, and taking a tank close to or below 6ph via the use of Co2 could in fact be actively detrimental. 

Also it begs the question of how much Co2 will the plant store and how much extra sugar would the plant produce as a result of higher Ph/RubisCo benefit at the end of a photoperiod. Would this be significant? Perhaps the lower your Ph, the more benefit you would see from this method as well as from longer photoperiod. 🤔


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## Libba (4 Oct 2022)

Count me as another adherent to the twelve-hour photoperiod philosophy. To be honest, I'm less concerned with optimal conditions, I just like to be able to observe my tank when I'm working from home and into the evenings. Any extra algae grown as a result is just more food for my appreciative ramshorn and bladder snails.


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## MichaelJ (4 Oct 2022)

Libba said:


> Count me as another adherent to the twelve-hour photoperiod philosophy. To be honest, I'm less concerned with optimal conditions, I just like to be able to observe my tank when I'm working from home and into the evenings. Any extra algae grown as a result is just more food for my appreciative ramshorn and bladder snails.


Yes,  and I think any algae issues are much more about stability, proper maintaince  and light intensity rather than the long hours of light by itself... as said, I have zero algae to speak of and run my lights for +12 hours in both my tanks. 

Cheers,
Michael


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## eminor (6 Oct 2022)

i never had success with high tech tank with more than 7 hours of light, it always end up with algae, in low tech i go up to 16 without problems, high tech is another world

I run ~300+ PAR for 6 hours


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## Yugang (7 Oct 2022)

JoshP12 said:


> I reckon the increased pearling didn’t happen day 1, but a few days or even a week after?


I am afraid I don't have a scientifically valid answer, but I was surprised how fast I saw a change. I would say in my case I saw already change on day 2 and 3 after increasing the light period. I am challenging my own observation here, as I would expect more time for the plants to adjust and take the benefit of the longer period.



KirstyF said:


> Just curious! Can I ask what is the RubisCo relationship with Ph if anyone knows


I recently researched various articles on photosynthesis, and if any conclusion from that it is that I am only more confused and/or that it all depends on the plant species and its machinery to capure inorganic carbon.


Yugang said:


> What I learned, and is of course obvious to the more educated members here , is that aquatic plants have developed a wide variety of adaptations to a changing environment (water depth, turbidity, light reaching the leaves, pH, CO2 and HCO3 sources, emersed/submerged, flow, etc) and how they balance the three main photosynthesis pathways C3, CAM and C4. There is a variety of mechanisms at play, and at at best any scientific article compares 2 or 3 plant species. It seems impossible to make scientific statements that are true for all aquatic plants, or even to all plants in our tank. Every plant is different when it comes to adaptation to dissolved inorganic CO2, and Rubisco is only a part of the story.


So the only thing I could contribute @KirstyF is that the water chemistry of CO2/HCO3 is pH dependant, and that the process of the plant capturing inorganic carbon (which involves more than Rubisco) differs from species to species, and may for each plant species have a different optimum with regards to pH.


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## JoshP12 (7 Oct 2022)

Yugang said:


> I am afraid I don't have a scientifically valid answer, but I was surprised how fast I saw a change. I would say in my case I saw already change on day 2 and 3 after increasing the light period. I am challenging my own observation here, as I would expect more time for the plants to adjust and take the benefit of the longer period


But it wasn’t instant! And I think that’s cool. Means it did adapt?

@KirstyF What Is the Role of Pigments in Photosynthesis?

Couldn’t find a paper quickly but the papers eluded to Mg concentration and pH.

That website - however reliable - said this:
RuBisCO is the key carbon-fixing enzyme in the process of photosynthesis, and it functions optimally at a pH of 8.


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## Yugang (19 Oct 2022)

Yugang said:


> It is a bit early to celebrate, mysteriously several plants that used to do very well have been stuggling recently.





dw1305 said:


> I don't really see how 18 hours of darkness can be optimal for any plant.


How true.

Two weeks later, I can definitely confirm that my short 6 hours photo period has had a significant negative impact. I went to 9, then 10 and see clear positive evidence of improved plant health. Went for some fun plant shopping, and they all feel happy in their new home. I don't believe the short photoperiod was harmfull for all plants, as my overall tank health was reasonable with several plants in top shape. However some other plants, that I usually could grow easily, had stunted or even died. 

My take away is that a 6 hours photoperiod is pushing several plants to their limits and is generally too short (at least in a high tech tank).


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## jaypeecee (19 Oct 2022)

oreo57 said:


> No, it doesn't work like that..


Hi @oreo57

Thanks for the Tokyo article - very en_light_ening.

JPC


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## jaypeecee (19 Oct 2022)

eminor said:


> I run ~300+ PAR


Hi @eminor 

May I ask how you measure PAR?

JPC


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## eminor (19 Oct 2022)

jaypeecee said:


> Hi @eminor
> 
> May I ask how you measure PAR?
> 
> JPC


hi, i had access to MQ-510 par meter from a friend, average par was between 240 and 310


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## jaypeecee (20 Oct 2022)

eminor said:


> hi, i had access to MQ-510 par meter from a friend, average par was between 240 and 310


Hi @eminor 

Many thanks for the feedback. If, and when, I purchase a PAR meter, it will also be from Apogee Instruments.

JPC


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## eminor (20 Oct 2022)

jaypeecee said:


> Hi @eminor
> 
> Many thanks for the feedback. If, and when, I purchase a PAR meter, it will also be from Apogee Instruments.
> 
> JPC


One of the best yes


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## Yugang (27 Oct 2022)

Yugang said:


> Just a few days ago my Juwel HeliaLux controller broke down again (second time in three years ), I put the lights on a simple timer and have now a more accurate 9 hours full light + 3 hours half light (and the spectrum equivalent of a cheap LED light).


I want to give a thumbs up to Juwel, great customer service and FOC solution for the problem - even on a 3 years old product. 👍👌
Also new firmware with improved functionality. I am in love again with my HeliaLux 😍


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