watertown28 said:
Yeah the 15 dollar investment is not what I was worried about IMO. I can still get em no problem. Cheap enough really.
Now that your doing a very fine job and swaying me to go back to the standard strip lights again, I do have a question... I see the there are 8k bulbs where I live that are handy to buy....would that be a better option providing more of the colors the plants might need?
No, probably not. I'll explain. First a note on Kelvin. This is the measurement of colour temperature as we perceive it. Light around 6000K [forgotten the actual number, it is just under 6000K if memory serves me] is the closest in colour rendition to the sun at mid-day. Light with a lower K, say 4000K or 5000K, has more red in the colour mix, and less blue, giving a "warm" white. Light with a higher K has more blue and less red, giving a "cool" white. Tubes intended for reef tanks must be primarily blue, hence the actinic and others have very high K numbers, 11,000K and such.
Aquatic plants require red and blue light to drive photosynthesis. This is why the so-called "plant" tubes and "aquarium" tubes frequently are primarily (if not exclusively) high in red and blue, giving a sort of purplish or sometimes goulish hue to the aquarium. I have in the past used these lights for several years. In addition to the odd colour hue (which I admit some aquarists like, but I do not because it is not "natural"), these tubes are for some reason much less intense, and algae is often a problem. Controlled studies have proven that light strong in the red, blue and green areas promoted the best response in plants. The tubes termed "Daylight" that have a Kelvin around 6000K to 7000K provide this.
Diana Walstad discusses this in her book, and surmises that this may be due partly to the increased intensity of the "daylight" tubes, but also may be due to the presence of high green. Plant leaves reflect light according to their colour, so red leaf plants are reflecting more red light in order to appear red, and green leaf plants reflect green light in order to appear green, and so forth. For this reason, many assumed that green light was not significant, and as it is not a driver of photosynthesis, this made sense. But as the tests have shown, there must be more to this. Diana also points out that the sun at mid-day when it is strongest on plants is high in the green as well as red and blue. So all this seems to support the test results that plant response was strongest to light between 6000K and 7000K. On single tube tanks, I always use a tube like the Life-Glo which is 6700K, or ZooMed's Ultra Sun which is 6500K.
With dual tube fixtures, one can expand from this without detriment to the plants, if not carried to excess. I personally like the "warmth" the 5000K adds as this brings out the reds in plants and fish a bit more. For several years I used a combo of one 6500K and one 9000K or one 10,000K on one tank. The plants were fine, though I did notice algae was a bit more prevalent. Since I have gone back to the 5000K/6500K combo, algae has been less of an issue. Light that is too high in blue is more likely to promote algae. Remember, the plants need blue but also red to photosynthesize, and if the red is insufficient in balance with the blue, the plants can only slow down, allowing an advantage to algae. I've experimented enough with this to be certain of the results.
Byron.