Dear All

After reading Tom's post about Light intensity in ADA tanks it is clear that when it comes to light for planted aquaria ,More is not equal to better.

Another factor in planted tank Lighting is duration of lighting or Photoperiod.

I am trying to find out what will be optimum duration of lighting for a planted tank.
There must be some point in time after which plants stop photosynthesis .

If someone can share their experience it will be of great help.

Regards

ame

I am not sure on the exact figure, but most say 12 hours is plenty, and there is no need to go beyon that point.

One bit of evidence is that some plants start closing up leaves when their preferred photoperiod is over. As I recall that has been found to be 8 - 10 hours.

I've heard that too. My latest 29 gallon low tech tank gets 9 hours of about 2.5 WPG, shows reasonable plant growth, and has no significant algae problems. I have a feeling that if I increased the period to 12 hours I'd start seeing more algae growth.

Bill

Hello Friends

I have also read and followed 12,10,9 Hours of photoperiod but these again are mostly approximation like the ones we all had about Light intensity(2,3,or 5 WPG).

After Toms findings on Intensity may be we should re- think our ideas about Duration as well.

Our assumption that plants need the same amount of light intensity for this entire period of 12/10/9 Hrs may also not be perfect.

Hope Tom will read this post and enlighten us.

Thanks to all for sharing their knowledge.

Regards

ame

Hi all,

With regards to preferred photo period, are we talking about total light intensity a plant receives? Or just 'wake up' time? Or even 'awake' time?

Case 1
Max light intensity for plant for 1 day = X micromol
If we lower the light intensity, are we able to keep the lights on longer??
This will vary the photo period drastically.
A 5WPG might need to have his lights on lesser than a 1WPG???

Case 2
I read that plants will start to 'wake up' 4 hours after continuous light and start photosynthesis. When does the 8-10hr countdown start from now?
Eg. Lights on @ 8am --> photosynthesis start @ 12pm --> plant leaves close @ 8pm regardless if light is still on.

Comments?

Regards,
Ryan

P.S. Ame, I hope you are not offended by my interruption, the low lighting thread has thrown my previous beliefs into the trash can. There are so much more to explore just on lighting alone.

Dear Ryan

Good to know that we think alike.

"so much more to explore just on lighting "-I couldnot agree more.

I am hoping that someone who has tested and tweaked their light duration and intensity together will be able to show us a way.

Well looking at nature and the sun's variation in intensity over the day we can get an idea that plants do not photosynthesize all day long.

I asssume we should start the day with low intensity light and increase it progressively till noon and after 3-4 hrs of max light should reduce intensity.

But this is an assumption how do we get facts ?

Will the plant guru's share their expertise?

Thanks in advance .

ame

Before running down the path of duration and intensity and modifying anything.........

Back up...............what is it that you want to do with plant growth?
Do you really and honestly want more growth and faster growth rates?
The whole point of reducing light is to reduce growth rates and demand for CO2 and nutrients.

Keep that in mind here.

If you want to increase the rate of growth, then perhaps.............but simply increasing light, or adding a bit more during part of the day is pretty simple and straight forward.

As few aquarist ever do dry weight analysis, you really cannot do much comparing with one light treatment vs another, but you can likely predict the outcomes if all else is equal(rare in most cases, but you might spot some trends as mentioned above, more light = more growth).

"Optimum light" assumes => more growth/faster growth and mostly maximum growth.

I'm not sure folks want that.
The trade off folks seem to tell me and others................... is that they want managed growth, so grow some things in at low stable light, then a bit of fast at max growth, then reduced light to reduce growth once filled in good.

Or have a bit more patience and have a slower growth tank.
Few ever asked for the fastest growth

If a farmer ask for optimum yields, this means the most dry weight harvest. For us it would mean that X plant light treatment has a higher weight/color, pigment, seed production, development etc than say plant treatment Y.

Just be careful is the question asked, ask "what is the real thing I am looking for?".

Regards,
Tom Barr

Hello Tom

Thanks for the reply.

What I meant by "Optimum Light" is the minimum amount light to grow healthy plants.

After you opened our eyes about light Intensity, may be we can also test our age old belief about light duration.

What do I want ? Exactly what most folks want i.e " managed growth, so grow some things in at low stable light, then a bit of fast at max growth, then reduced light to reduce growth once filled in good"

Say for my 4ftx2ftx21 in tank I decide on 4 ,54W T5. If plant growth is not limited by light intensity(other factors adequate ,not limiting ) then will it be limited by Light duration ?

If I chose to reduce light duration to say 9 hr will that be a limiting factor ?There must be some duration above which light is wasted and some duration below which light will limit plant growth. That duration is what i meant by "Optimum period".

The whole idea is to grow healthy and good looking plants but not to waste electricity and minimise water heating due lights( my water temp reaches up to 32C in summer)

Thanks once again for the work you have done .

Regards

ame

Hi,

as Tom has pointed out every so often we should ask ourselves first what we are looking for and what our goals are before we make any decisions. As far as I am concerned I prefer a way of lighting which has seldom been dicussed so far. Most important for me is change. Change of light during the daily photoperiod like it's happening outside our glass boxes (both in intensity and color) in order to see fish and plants under different lighting conditions. I therefore have staggered intensities beginning and ending the photoperiod with very low light. After the dimmed start there is some more light then another increase before the highest blast begins (4-5 hrs only). Stepping intensities down is staggered the same way.

Total photoperiod lasts about 13,5 hrs including a very low light period at the beginning and end of each day (2,5 hrs together). This not only allows me to observe flora and fauna much longer but also under different intensities and shades of color (I am using ADA bulbs and Giesemanns "midday" which render the most pleasing combo to my eyes). Plants are very capable of adapting to different conditions so this has given me no problems in plant (or algae) growth at all as long as the high intensity blast does not exceed 5 or 6 hrs.


Best regards,
Detlef