To make a comparison, the sun in our Northwest Ohio region, open prairie, in
June recieves 1100 5Mols7m27sec. He would shade from that point down. All
the way to 400 5Mols7m27sec, which was a point where death became an issue.
The 400 watt metal halides I was using to make all my _tropical_ corals and
macroalgaes grow and glow only registered in at 600 5Mols7m27sec in the open
air!!! This is stuff that lives in 4' of water under the Fijian sun, where
it's more accepted that the values there above the water surface are 2000+
5Mols7m27sec !
We discovered this as we were trying to conserve energy and use metal halide
to light our baby lupine and New Jersey tea plants instead of running a
bazillion flourescents. It worked out okay because we were only mimicing
the April sun, and the discrepantcy in light worked out to be "75% shade".
So much for that Tim the Tool Man Taylor "Reah rreeee grot prooower huh huh
huh!" :)
But it blew my mind that something I thought I was _scorching_ was getting a
severely reduced amount of light energy due to reflection at the water
surface, refraction in the column, minerals and any organic matter absorbing
the photons.
I think we can extrapolate that to create this kind of color from the
tropics:
http://www.farmertodd.com/images/Shawn/DSCN2201.JPG
That these coral have evolved to receive about 20-25% of the available PAR
intensity, even in shallow depths! Most of these corals are hermatypic fore
reef, back reef animals. I think only the reef crest ones are those who can
really take the beating (that 2000 number), as low tides as spring and fall
have them actually exposed to the full sun.... They have evolved coping
mechanisms tho (pigments, slime, etc) I'm sure there's a study
somewhere....
So, 3% of the radiation at northern latitudes, in tannic and or organic
loaded water... Yep, that makes a ton of sense.
Here's a nice site I found while poking around refreshing myself on units
and stuff. Might be worth a looky.
http://www.coralreefecosystems.com/ltg_technical_data.htm#Spectral%20Distribution
Todd
----- Original Message -----
From: "Bruce Stallsmith" <fundulus_at_hotmail.com>
To: <nanfa_at_aquaria.net>
Sent: Monday, February 02, 2004 6:51 PM
Subject: Re: NANFA-- 135 gal. Freshwater Tank
> OK, and I went back to another source, too, Wetzel's book "Limnology" to
see
> what the received wisdom about submerged macrophytes (big, real, plants)
is
> for temperate natives. A key point he makes is that "submersed macrophytes
> are distinctly shade-adapted with high concentrations of pigments and
> low-light compensation points of photosynthesis, commonly at 1-3% of full
> sunlight." Their light physiology is comparable to shade-dwelling land
> plants, like most ferns or Selaginella. They often suffer from
> photoinhibition at higher levels of light, i.e. there's such a thing as
> hitting them with too much light.
>
> I realize that this is a very different view than coral reef tanks, where
> the algal systems need to be driven with really intense lights, or even
the
> standard tropical set-up. So I'm happy for the moment to be using 460 nm
> actinics, and hit the plants with a steady source of blue/green wavelength
> light. I'll soon know if this set-up is good for good ol'
photosynthetically
> active radiation.
>
> --Bruce Stallsmith
> Huntsville, AL, US of A
>
> >From: "Todd Crail" <farmertodd_at_buckeye-express.com>
> >Reply-To: nanfa_at_aquaria.net
> >To: <nanfa_at_aquaria.net>
> >Subject: Re: NANFA-- 135 gal. Freshwater Tank
> >Date: Mon, 2 Feb 2004 18:18:54 -0500
> >
> >You know I think I can do this really quick. :)
> >
> >Get a lamp color between 4000K and 6500K and the plants will do just
fine,
> >and will be well within their zone of photoreactivity to outcompete the
> >algaes.
> >
> >There's nothing to analyze there!
> >
> >How much carbon and micronutrients you have to provide to meet the uptake
> >depends on the amount of PAR (Photosynthetically Available Radiation) you
> >are providing. This is a measure of intensity.
> >
> >If you have more PAR than available carbon and micronutrients, you will
> >open
> >the door for algae to participate, regardless of what lamp color you
have.
> >
> >If you have less PAR than available carbon and micronutrients, uptake may
> >not be fast enough due to an "energy input" deficincy to use the
phosphates
> >and nitrates our aquariums produce, and you will open the door for algae
to
> >participate, regardless of what lamp color you have.
> >
> >High Color Temp has lower PAR values as the wavelengths are long and
> >infrequent. Low Color temp has higher PAR values as the wavelengths are
> >short and more frequent.
> >
> >Flourescent and Compacts have lower PAR values because the wattage is
> >derived along a tube. Metal Halide has high PAR values because the
wattage
> >is derived from a tight source point.
> >
> >Yes, it's a balancing act, and you have to figure it out yourself. No
one
> >can teach this, regardless of how many act like they can.
> >
> >And more info to arm you...
> >
> >At similar wattages, Metal Halide has a very short but square intensity
> >footpint... Flourescent lamps have thin but long intensity footprint.
> >
> >Flourescent lamps are good for achieving a like lower intensity across a
> >large area which is good for most submerged plants commonly found in our
> >hobby.
> >
> >Metal Halide is good for achieving something that looks like sunlight,
can
> >be filtered by emmergent plants and still reach the submerged plants
below,
> >reflected off of wood to produce shadows, and meet a whole realm of plant
> >community requirements.
> >
> >Todd's book of lighting in 8 minutes! Heck yeah! :)
> >
> >Hope this helps..
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