glazing material & UV - revisited

[karburn]

I did a search first for threads on greenhouse glazing materials and UV filtering, but most were older threads and none specifically dealt with what type, brand, rating, etc., of material would be preferable for a greenhouse. Now that I've got my electric panel upgraded and have a generator back-up installed, the next step is a small starter greenhouse - likely a kit like RION in a 8 x 24 size. How do you determine if the glazing material is acceptable or not? No one wants to use something that will screen out too much beneficial light for the corals. I remember that there are ratings for plexi, but how bout greenhouse mfrs? Any leads are appreciated. Hope to move out of the basement next spring - the inventory has out-grown the space!!!

[rick rottet]

FWIW, this is some of what I have learned during the research for my greenhouse. To be sure, I still need to keep learning as I go. Most of the so-called "clear" glazings that I checked out will block UV up to ~360 nanometer wavelengths.

Now it's time to start making this thing look like a greenhouse. The ends get covered first. I am using two layers of a poly film made by a company named Klerk's. I chose their 'KL-50 Clear' because it will filter UV light up to 360 nanometers in wavelength. We should all be aware that our target range for coral lighting is the 400-700 nm range (light that leans towards the blue end of the spectrum). Through some research, I found that UV-C (light in the 200-280 nm), while very destructive to life, is naturally filtered out by the earth's atmosphere and isn't significantly present on this planet but may be found in some high energy applications such as the light emitted from an arc welder or some UV sterilizer bulbs. UV-B (280-320 nm) is also destructive to tissue. UV-B is the light that gives us a sunburn. UV-A (320-400 nm) is what's needed to maintain the fluorescing pigments of corals, at least towards the upper wavelengths of that range. There were some studies which suggested that UV-A from 310-350 nm may be at least partly responsible for some bleaching events. Many corals can produce compounds known as microsporine amino acids (thick clear-ish or opaque mucous coat) which is basically a sunscreen that will absorb light in the 310-360 nm range. These compounds are absorptive pigments only and are not reflective so they do not contribute to a corals' coloration. I found that the reflective or fluorescing pigments, in general, were maintained with light around the 390 nm wavelength so this poly covering was almost perfect in that regard. By filtering out light less than 360 nm, most of the corals wont need to spend energy producing a "sunscreen" but will still have the wavelengths they need for coloration. The corals that need higher wavelengths can have screens placed above their tanks to provide the correct amount of light. Anyway, here goes the first layer of the greenhouse glazing on the north end.

If you're interested in seeing the whole thread, it can be found here
http://archive.reefcentral.com/forums/showthread.php?s=&threadid=465933

[karburn]

excellent information. Thanks very much!!!:)

[rick rottet]

You're welcome and good luck with your new project.