ame;30666 said:
Hello Tom
Thanks for the reply.
What I meant by "Optimum Light" is the minimum amount light to grow healthy plants.
Probably about 40-50micromols seems like a safe bet, you want a little wiggle room and not go to the bone here.
After you opened our eyes about light Intensity, may be we can also test our age old belief about light duration.
Well, 6-10 hours is the likely range that will help the most. Less than this, things drop off a bit. Depends on the species but in most cases, 8-10 is best for good efficient growth. You do not get the same results from adding 2x as much for 1/2 the time............it does not work that way.............
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 ?
It can. I think it will depend on many things also though, individual plant species species, reserves the plants in question have built up etc.
I can cover Crypts (no light measured at all) for a month and they do fine if they have access to light outside the cover. They are able to draw and translocate resources.
I think this was more your point/question, but think about algae though.............they need higher light in general, so adding high intensity but shorter time frames does not help there.
But you can get to the point where you start limiting plant growth via duration as well.
But..............I think working on intensity and sticking with 8-10 hours first and getting really well known in that area should be done first.
I have no examples of nice ADA scapes with 2-4-6 hour ranges available to compare with. Do you? Would you spend 10-20K and set them up and win in the top 20 in the ADA contest?
This was low picked fruit, but we already have a good consensus about the duration, yes, it can be manipulated but do you want to go down to the bone there? Plants can and do adapt to intensity pretty good, duration? Much less so and it will be tougher to say anything more than theories...............
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
8-10 hours ought to do it for most plants.
You can watch and see when they "close up", like Cabomba species, you might argue that that is a sign of enough duration and adding more light is not needed.
This does occur faster at higher intensity light. How much more? Maybe 7 hours vs say 11 if you stretched it to extremes. Maybe more if you went way down on intensity.
As you approach the edge of LCP's whether from duration and intensity or some combo of the 2, you really will have more troubles and issues as many species will have different tolerances. The nice thing about all this that I did, was the fact I had some nice scaped examples with a wide range of plants that I knew of and several replicates , as well as knowing the tanks and the folks's general care and routines. So I did not have to do much work to show the tanks needed little light in terms of intensity. To test what you seek, that's a lot of work and I am not that motivated to do it, you are certainly welcomed to do it however
Regards,
Tom Barr