# Why is 8 hours a day the general aquascape lighting rule?



## DutchMuch (Apr 12, 2017)

Why is 8 hours a day the general guideline to have lights on in your aquascape?
I personally have mine on for 8 hours with great results but im just pondering the subject. 
I would think its because algae and plants both take in bioavailable carbon and with under 8 hours of light (the considered bare minimum for plants) would be because anything lower than 8 hours algae is getting more of the carbon and light than plants depending on its dispersion?


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## Maryland Guppy (Mar 5, 2015)

I have always ran a 6.5 hour photoperiod.


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## Dr Wakin (Jul 4, 2018)

I ran mine between 9-10 hours.


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## hoppycalif (Apr 7, 2005)

As I recall many people used to use 12 hour photoperiods. It became evident that those who did that had more algae problems than those who used shorter times. So, it became "common knowledge" that 8 hours was the optimum photoperiod. I can't recall anyone actually doing a controlled experiment to look for the real optimum photoperiod. Instead, people began trying the idea of splitting the photoperiod into two equal short time periods, and not much discussion occurred after that about optimum photoperiods.


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## Dr Wakin (Jul 4, 2018)

For people running more than 8 hours like me were mostly using low lightnings. Infacted 10 hours is just nice for my low light tank. IMO, there's no definate set of rules for photo period as all tanks were different also their husbandry. A friend of mine running anoxic filtration could get away with zero algae literally. Maintaining nitrates at a constant 0-5ppm no water change ever needed just topping off daily. Daily starting off at 5ppm or less, reaching mid day till end of photo period 0-3ppm. Overstocked tank but heavily planted.


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## tiger15 (Apr 9, 2017)

I have asked the same question when I started my first planted tank a year ago. Tropical plants get about 12 hour sunlight daily, and subtropical and temperate plants get even longer sunlight in summer months. So why provide only 8 hour photo period.

Experienced plant keepers have demonstrated that they can grow lush plants with no algae for as short as 6 hours lighting. They argue that plants get their fill in the first 4 hours and slow down photosynthesis thereafter and stop after 8 hour. Folks who grow high light plants notice that stems close up after 8 hours and any further lighting will be a waste. I don't grow stems, only low/medium light rosette, ferns, anubias and Buce. They don't open or close up like stems so I have no way to tell if non-stem plants behave the same.

Another related question is one or split photo periods. Walstad tanks advocate split photo periods to allow natural recovery of CO2. High tech folks argue that split photo period is unnecessary with CO2 injection, and may confuse and interrupt plants into restarting photosynthesis. 

I do two 4.5 hour split photo periods daily to fit my life style regardless of the argument. 6 to 8 hour photo period in one chunk is too limited for my enjoyment as I don't want to see my tanks in darkness during my prime time at home.


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## mistergreen (Mar 3, 2007)

Yeah, it depends on the intensity of light you have. If you don't have good lighting, just extend the photo period. If you're getting algae, shorten the photo period.


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## hoppycalif (Apr 7, 2005)

mistergreen said:


> Yeah, it depends on the intensity of light you have. If you don't have good lighting, just extend the photo period. If you're getting algae, shorten the photo period.


But there is a minimum light intensity required for each species of plants to grow - the light compensation point. If the intensity is less than that it doesn't matter how long your photoperiod is, the plants will not grow. I don't think there is a table of light compensation points vs. plant species, or at least I haven't seen one.


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## mistergreen (Mar 3, 2007)

Yeah, low light intensity growth won't be optimal depending on the species but there would be some growth given nutrients, CO2.


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## kafkabeetle (Oct 11, 2011)

I wonder how inhabitants feel about split photoperiods. Like I wonder if it could be stressful to go through day and night in an unnatural rhythm. But then I suppose they could just perceive each time the light it on as a day regardless of how long and know no better...


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## hoppycalif (Apr 7, 2005)

kafkabeetle said:


> I wonder how inhabitants feel about split photoperiods. Like I wonder if it could be stressful to go through day and night in an unnatural rhythm. But then I suppose they could just perceive each time the light it on as a day regardless of how long and know no better...


Until they stage a demonstration, with signs and chanting, I wouldn't be concerned.


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## kafkabeetle (Oct 11, 2011)

Wow...


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## kafkabeetle (Oct 11, 2011)

I thought it was a valid question, as many of us go to great lengths to replicate natural environments as closely as possible. Animals flip out before an eclipse when light patterns are different from what they are used to. Why so dismissive?


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## DutchMuch (Apr 12, 2017)

kafkabeetle said:


> I thought it was a valid question, as many of us go to great lengths to replicate natural environments as closely as possible. Animals flip out before an eclipse when light patterns are different from what they are used to. Why so dismissive?


tbh I dont think hoppy meant to come off rude  think you just took it that way. 
Hes saying he doesn't think itll be an issue.


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## kafkabeetle (Oct 11, 2011)

I mean whatever but I actually do sweat things like that, to the extent that I've been looking for an affordable light that's compatable with a ramp timer to simulate sunrise and sunset. I think a lot about how to create the least stressful conditions for all the animals in my care. Not saying it's necessarily a big deal but I thought it was worth some discussion at least and it was a serious question.


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## DutchMuch (Apr 12, 2017)

kafkabeetle said:


> I mean whatever but I actually do sweat things like that, to the extent that I've been looking for an affordable light that's compatable with a ramp timer to simulate sunrise and sunset. I think a lot about how to create the least stressful conditions for all the animals in my care. Not saying it's necessarily a big deal but I thought it was worth some discussion at least and it was a serious question.


In my own opinion, I think it was stress them out for the first week it happened. Throughout the week lowering the shock to the lights effect. 
Eventually getting them used to it.


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## tiger15 (Apr 9, 2017)

kafkabeetle said:


> I wonder how inhabitants feel about split photoperiods. Like I wonder if it could be stressful to go through day and night in an unnatural rhythm. But then I suppose they could just perceive each time the light it on as a day regardless of how long and know no better...


I have morning and evening split photo periods, and the fish love it. As soon as the light is on, the fish are dancing in the front anticipating that food is coming soon. It's my routine to feed my fish breakfast and dinner twice a day. It's not total darkness in between photo periods as there ambient room light.

I am not sure what the plants feel or they have feeling at all. Some say that split photo periods would confuse plants photosynthesis rhythm. I have to see evidence to prove it as in nature, there are cloudy episodes and photo periods do not run in clockwork.


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## dwalstad (Apr 14, 2006)

tiger15 said:


> I am not sure what the plants feel or they have feeling at all. Some say that split photo periods would confuse plants photosynthesis rhythm. I have to see evidence to prove it as in nature, there are cloudy episodes and photo periods do not run in clockwork.


Here, I hypothesize that plants can easily handle a few hours of darkness with split photoperiods. In nature, it's afternoon shading from overhanging trees, a few hours of cloud cover, etc.

There was a question in my mind that if the Siesta was in total darkness that the plant might become confused- think that it was time to go to bed and shut down photosynthesis.

Experiments with terrestrial plants and daylength suggest that they don't. For if a 16 hr totally dark period is interrupted by even one minute of bright light, investigators found--much to their surprise--that the plant behaves as if it was not night-time. So if we subject our plants to 4 hr of light, then 4 hours of total darkness, and then 4 hours of light, I believe the plants may behave as if they were getting a 12 hour daylength. That is, they don't "shut down" during that 4 hr of darkness.


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## Maryland Guppy (Mar 5, 2015)

I have often thought of creating two photoperiods within a 24 hour day.
Would plants grow twice as much?
Would I really want them too?
Trimming could be a nightmare?


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## DutchMuch (Apr 12, 2017)

Maryland Guppy said:


> I have often thought of creating two photoperiods within a 24 hour day.
> Would plants grow twice as much?
> Would I really want them too?
> Trimming could be a nightmare?


Increase of sales


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## Maryland Guppy (Mar 5, 2015)

I don't care how much I sell.
But I hate to throw it in the trash.

If items go for half price or even a quarter of the price someone gets to experience the growth!


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## DutchMuch (Apr 12, 2017)

Same here I rather do it for free than toss stuff lol,
now I need to make a meme of shia lebouf and ill brb


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## DutchMuch (Apr 12, 2017)




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## tiger15 (Apr 9, 2017)

dwalstad said:


> Here, I hypothesize that plants can easily handle a few hours of darkness with split photoperiods. In nature, it's afternoon shading from overhanging trees, a few hours of cloud cover, etc.
> 
> There was a question in my mind that if the Siesta was in total darkness that the plant might become confused- think that it was time to go to bed and shut down photosynthesis.
> 
> Experiments with terrestrial plants and daylength suggest that they don't. For if a 16 hr totally dark period is interrupted by even one minute of bright light, investigators found--much to their surprise--that the plant behaves as if it was not night-time. So if we subject our plants to 4 hr of light, then 4 hours of total darkness, and then 4 hours of light, I believe the plants may behave as if they were getting a 12 hour daylength. That is, they don't "shut down" during that 4 hr of darkness.


It's only hypothesize, until it can be proven by control experiments.

In terrestrial plants, nurseries have been playing with green house lighting to fool plants into blooming at wrong time. I don't know how manipulation of lighting can affect vegetative growth. Furthermore, experimental results in terrestrial plants may not be transferable to aquatic plants.

Hobbyists have observed that stem plants can take no more than 8 hour lighting and will close up beyond that. So splitting 24 hours into 8 hour lighting alternating with 8 hour darkness theoretically double the growing time, but will it increase or reduce growth rate, increase or reduce algae? Only careful control experiments can tell and even so, experimental results of stem plants may not be transferable to non-stem plants.


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## DutchMuch (Apr 12, 2017)

tiger15 said:


> Hobbyists have observed that stem plants can take no more than 8 hour lighting


ive been in this hobby a few years.. ive been around the corner, never have I seen a statement as false/out of this world as this. (I hope your talking about emersed plants and not submersed plants)
Ive seen tanks (which I dont personal promote) with people who for some reason keep their lighting on 12/hrs and stem plants continue to open and photosynthesis, weather its HEALTHY or not I couldn't tell you but I can tell the growth was as lush as something in my own tank which has 8/hr lighting.

Edit:
just tried looking up some articles about the quoted comment, couldn't find any results.


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## hoppycalif (Apr 7, 2005)

"Stem plants" includes a lot of different plants, and there is no reason I know of to assume that all of them react the same way to longer or shorter photoperiods. I do know that some species of stem plants do close up after about 8 hours of light - that has been noticed by many hobbyists. Unfortunately I don't remember the specific species that acted that way. We hobbyists, most of whom are not scientists, used that data to enforce our belief that 8 hours is a good photoperiod, and 12 hours is too long a photoperiod.

Anyone who wants more information on this can very likely find it, with a fairly simple Google search. If anyone does it, please share what you learned!


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## dwalstad (Apr 14, 2006)

According to one aquascaper, algae is almost "impossible to control" with photoperiods longer than 8-9 hours. Perhaps it is a relatively recent change due to the intense light provided by LEDs. In the "old days," 12-14 hours was fine.

AS to plants folding up, below is link to a nice discussion. As the thread goes along, hobbyists (including Tom Barr) mention many species. Also, one authority sent me a picture of _L. belem_ with folded leaves; the plant folded its leaves before the lights went out.

https://www.plantedtank.net/forums/...atic-plants-fold-their-leaves-up-night-2.html


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## DutchMuch (Apr 12, 2017)

dwalstad said:


> According to one aquascaper, algae is almost "impossible to control" with photoperiods longer than 8-9 hours. Perhaps it is a relatively recent change due to the intense light provided by LEDs. In the "old days," 12-14 hours was fine[/url]


hm, I think saying its impossible to control over 8+ hours is a pretty broad spectrum youd be walking into. I have to respectfully disagree. I think if you've slowly ramped up that time- which ive seen people with some killer tanks do- not losing your tanks equilibrium, and not adjusting anything else- you would be fine. You might have to adjust fertilization though however thats a different story. Now algae being Unpredictable is a given in all setups.


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## hoppycalif (Apr 7, 2005)

dwalstad said:


> According to one aquascaper, algae is almost "impossible to control" with photoperiods longer than 8-9 hours. Perhaps it is a relatively recent change due to the intense light provided by LEDs. In the "old days," 12-14 hours was fine.
> 
> AS to plants folding up, below is link to a nice discussion. As the thread goes along, hobbyists (including Tom Barr) mention many species. Also, one authority sent me a picture of _L. belem_ with folded leaves; the plant folded its leaves before the lights went out.
> 
> https://www.plantedtank.net/forums/...atic-plants-fold-their-leaves-up-night-2.html


Thank you for finding that TPT thread! I remember it very well, and I think it is what convinced me that 8 hours is the optimum photoperiod. (I am not a scientist!!)


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## tiger15 (Apr 9, 2017)

Hobbyists who reported stem plants close up after 8 hours have high light systems in majority. Walstad systems are majority low/moderate light systems that can't grow stems except for a few easy ones. So the deduction that 8 hours is the maximum plants can take is relevant to stems but not necessarily to non-stem plants.


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## DutchMuch (Apr 12, 2017)

tiger15 said:


> Hobbyists who reported stem plants close up after 8 hours have high light systems in majority. Walstad systems are majority low/moderate light systems that can't grow stems except for a few easy ones. So the deduction that 8 hours is the maximum plants can take is relevant to stems but not necessarily to non-stem plants.


that would be relevent only to a certain setup type
and even then i have seen different Thousands of times. go check our the journal sub forum here, some are NPT's with lights on for over 10+ hours (same for the ladder)


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## hoppycalif (Apr 7, 2005)

tiger15 said:


> Hobbyists who reported stem plants close up after 8 hours have high light systems in majority. Walstad systems are majority low/moderate light systems that can't grow stems except for a few easy ones. So the deduction that 8 hours is the maximum plants can take is relevant to stems but not necessarily to non-stem plants.


It is probably not relevant for all stem plants, whether high light ones or low light ones. There must be 100's of stem plants available to us now, so it is a pretty safe bet that not all of them react badly to longer photoperiods. But, I do think it is also a safe bet that 8 hour photoperiods are adequate for most of the stem plants. And, for sure, it is easy to use a shorter or longer photoperiod if we want to.


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## Ranger88 (11 mo ago)

Quote "Tropical plants get about 12 hour sunlight daily, and subtropical and temperate plants get even longer sunlight in summer months"
----
I question the assumption that tropical aquatic plants get 12 hours of sunlight naturally in the wild. It's possible since daylight is closer to12 hrs consistently being closer to the equator, but these submerged plants are in bodies of water that have tall canopies of dense terrestrial vegitation growing right to the waters edge. That could mean that early morning and late afternoon sun is blocked and fully shaded on the body of water. Only mid day sun (8 to 6 hrs) would shine direcly into the water. What do you think???


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## Michael (Jul 20, 2010)

Welcome to APC!

The most recent post in this thread is from 2018. It is unlikely that you will get any replies. Why not start a new discussion on the topic?


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