# Is a 12 hour photoperiod okay?



## Darkblade48 (Jan 4, 2008)

12 hours is definitely a bit long, even if you have low lighting. I would perhaps use around 8-10 hours, and monitor to see if there is an algae (and adjust accordingly)


----------



## Aesyir (May 10, 2017)

Would it be okay to change the time all at once or gradually do it.


----------



## discuspaul (Jul 27, 2010)

Why not change it all at once, so as to not prolong the period when algae can continue to grow and accumulate.
Drop it to say, 7 hours/day immediately and see how that amount of lighting works to your liking over time.


----------



## Darkblade48 (Jan 4, 2008)

Aesyir said:


> Would it be okay to change the time all at once or gradually do it.


It is fine to decrease the photoperiod in one go.


----------



## Quagulator (May 4, 2015)

While 12 hours off the get go is a little long, each tank is different and can handle different length of light. All my low tech tanks are in excess of 12 hours, usually about 14 hours a day no ramp up ramp down, just on/off. But, these tanks did not start with that much, I gradually increased the length as the plants grew in. I would much rather start with too little than too much, because as everyone else has said, algae can be an issue.


----------



## AbbeysDad (Apr 13, 2016)

I could be wrong, but I think the best photo period depends on several factors....

> the intensity of the light. 
> the height of the tank.
> the light distance above the tank.
> the amount of supplemental (room/sun) light.
> the cleanliness of the canape (if used).
> the clarity of the water.
> the types of plants.
> the use of injected CO2.
> the amount of ferts.
> high tech / low tech.

So many variables dictate the best photo period. There is no one size fits all.
Basically too much light likely encourages algae and too little light stifles plant growth.

footnote: My light is on from 6am until midnight - 18 hours! (Finnex Planted+ 24/7 in 24/7 mode)


----------



## houseofcards (Mar 21, 2009)

As with most things in planted aquaria, your dealing with a set of variables as pointed out by @AbbeysDad would have countless combinations that would make it impossible to tell you how long to run a photo period. Always best to start off with a shorter period and move up from there and see how much the system can tolerate. Sames goes for water changes, etc.


----------



## MultiTankGuy (Jan 8, 2018)

Aes...

12 hours is fine for tropical aquarium plants. Most originate in areas with long hours of daylight, so they're used to the tank lights being on for a long time. I keep elodea (Anacharis) and Hornwort in some of my tanks and floating plants thrive in longs hours of daylight and floating close to their energy source (light). These are easy to grow plants, so they don't need added CO2, they'll get plenty from the surrounding air. Keep the tank water clean and mineralized with large frequent water changes. This will replenish minerals that are changed or lost to filtration and used by the fish and plants.

M


----------



## jeffkrol (Jun 5, 2013)

You can run lights 24/7 if one chooses (counter-intuitive but its true).
t


> here is no wrong veg schedule.....24/0, 20/4, 18/6 etc.
> 
> personally i perfer the 20/4 OFF, then they get some dark time.....ppl say it's not necessary but i happens in nature....so i figure why not.
> Problem is you generally run out of something else.. nutrients/CO2 causing a horrible imbalance..


Ask an "herb" grower.. 

If the tank is running fine now and you don't WANT to change things.. change intensity proportional to time interval..

i.e 50PAR at 8hrs (16.6 DLI) = 33PAR at 12 hours (16.5 DLI)..
"Should" keep things stable.. 
The importance of DLI - Greenhouse Management


----------



## The Dude1 (Jun 17, 2016)

That isn't what they teach in Grad school. Reactions are broken up into light and dark reactions. Dark reaction replenish some of the things utilized heavily in the light reactions NADPH being one. 
I haven't tested any of it, but that's what the people with Doctorates say.


----------



## houseofcards (Mar 21, 2009)

I'm not sure how the emersed references are helpful or have anything to do on a practical level with OP question. As you increase photo period you increase the likelihood of algae which is not a factor with terrestrial plants.


----------



## jeffkrol (Jun 5, 2013)

The Dude1 said:


> That isn't what they teach in Grad school. Reactions are broken up into light and dark reactions. Dark reaction replenish some of the things utilized heavily in the light reactions NADPH being one.
> I haven't tested any of it, but that's what the people with Doctorates say.


Mis-understanding.. Dark reactions occur in the light as well..
I said you could.. never said you should...



> 4 years ago
> 
> 
> Aaron I. Velez-Ramirez
> ...


https://www.researchgate.net/publication/50375084_Plants_in_continuous_light

Bump:


houseofcards said:


> I'm not sure how the emersed references are helpful or have anything to do on a practical level with OP question. As you increase photo period you increase the likelihood of algae which is not a factor with terrestrial plants.


Not if you decrease the intensity......
Hours don't mean anything really..only accumulated photon exposure..

https://www.google.com/url?sa=t&rct...%295-17o.pdf&usg=AOvVaw18LESSTFwiwszA1WVmH5Ic


> In this review an attempt has been made to analyze the results of the studies that explored the changes in the growth and devel
> opment of plants exposed to continuous light published since the 1930s, including papers that are available in Russian only. Potential be
> nefits of using a 24-h photoperiod for the production of greenhouse crops, transplant production in closed controlled environment systems
> and the culture of plants in controlled ecological life support systems are reviewed. Continuous lighting is shown to be a useful tool
> ...


----------



## houseofcards (Mar 21, 2009)

jeffkrol said:


> Hours don't mean anything really..only accumulated photon exposure..


Tell that to a carpet plant. :crying:


----------



## The Bungulo (Aug 28, 2017)

Like a few others have said, hornwort and elodea dont need Co2. I keep my light on from 7:30 in the morning till 9 pm. No algae problems exept for some on the anubias ive been trying to eradicate.


----------



## OVT (Nov 29, 2011)

Blaming light for growing algae is same as blaming light for growing plants.

But starting slow and bumping things up as you go has its benefits.


----------



## jordie416 (Jul 1, 2016)

Photo period duration mostly depends on lighting intensity. I would not run more than 8 hours on my high tech tank (Kessil lighting and high CO2). On my low tech tank (Current planted plus LED and excel, no CO2) I run lights for 10 hours. My lo wtech has no algae but my high tech gets GDA on from glass.

Not scientific but it is what works for me.


----------

