<a href=showthread.php?s=&postid=9224628#post9224628 target=_blank>Originally posted</a> by alizarin
Hi Ah64av8tor =)
As I understood it true actinics put out a meager amount of photosyntheticly active light (compared to your other lights) that actually reaches the zooanthelle. I was under the impression that zooanthelle use several peaks of light, the strongest are 420nm (blue) and 670nm (orange) and since it takes twice as many watts to make a lumen of blue than it does orange, the orange is much more usable per watt.
That makes a little sense at the surface or on land, the orange will have almost twice the par per watt, but the penetration through water is almost half at 1meter and diminishes exponentially with depth to almost 0 at 10 meters so its a wash.
When I went from 20k to 14k my coral growth improved. 14k to 10k it improved allot. When I added actinics to the 10k it didn't really do much except in the shadows since the 10k is a halide and is more directional than the T5s and one of the T5s is a "blue plus".
And if you went to a 6500k you would have seen even better growth only with out the color, you need the actinic supplementation too and Ill quote Bob Fenner
More blue really does help out with coral color. It excites and stimulates the corals to produce more pigments.
<a href=showthread.php?s=&postid=9224628#post9224628 target=_blank>Originally posted</a> by alizarin So I guess my position was that there's some benefit but not so much you'd see a change in your corals if you turned them off.
If you did a test you would find in the long run the corals without actinic supplementation would shift towards brown.
Bob Fenner who wrote "The Conscientious Marine Aquarist" said "The functionality of aquarium 'actinics' is minimal"
There are a few errors on the part of Bob Fenner and a few missunderstandings on your part also.
When asked
I was wondering which bulbs would give the aquarium a more blue color? 420? 460?
his reply was
The visible blue light has a wavelength of about 475 nm, indigo light has a wavelength of about 445 nm and violet light has a wavelength of about 400 nm. So It would stand to reason that 420 would give more of a purple tint and 460 would give more of a light blue.
I could pick this apart but there is no need to. Neither Anthony Calfo or Bob Fenner has or will say there is no need for actinic supplementation, but would say under certain situations it might not necessary.
For several years I have farmed corals under 6500k Iwasaki 250 Watt MH and always had super growth, but before I could sell or trade them I would have to color them up with actinic supplementation. I learned my lesson early and always use actinics with the daylight bulbs for good growth and color.
