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ok i just read a post below regarding Phillips Aquarelle tube,i know i dont have enough lighting on my 3 foot. only enough to grow low light plants. so my 66watts of light is still only 66watts regerdless of light spectrum levels??? so how does a 18watt 2800k compare to a power glo 18000k (which is one of my tubes i have currently as i thought this would be better than geting the Flora gro at only 2800k) I too have a aqua relle tube and thought this too was a good choice as its a 10000k. have i stuffed up my lighting with the wrong choices? my third tube is a Growlux 18watt (not sure of the spectrum level)

loulou,

The best light temperature to grow plants is around 6000 to 8000 K.

That's why freshwater fixtures, like the ones from Coralife, are sold with 6,700K power compacts. Anything above 10,000K is for sure not as efficient. I have no idea what a 2,800K would do .

Remember that plants have different "eyes" than humans. What we think is an efficient light might not be the best solution for the plants.

Hope this helps,

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club

Hi,
Now, you have hit on the "flaw" of using wattages for
determining the best lighting for an aquarium.

Every one of us has seen the difference between a 10 watt
nightlight and a 100 watt reading light. Or seen the
difference between a 40 watt bulb and a 100 watt bulb.

Watts, are a measure of power, and in the case of lights,
it is a measure of energy (electricity) consumed to make
a given amount of light. We have come to understand that
the higher the energy consumed (watts) the brighter the
light. This is true for all lights.

Simply put, the "WPG Rule" is an easily understood guidline
especially for beginners. It makes things simpler for them,
and us, and speaks in terms that we all have experiance
with.

Now, toss in the term "temperature" which is measured in
"Degrees Kelvin." Anyone who uses a gas torch and has
heated metal, or anyone who has an electric stove with
exposed elements, has seen that as you heat the black
object, it starts to turn red, then as it gets even hotter,
the red changes to yellow, and then to white, and even
hotter to a bluish white. (Of course the stove only
goes through red but the red will get to become a brighter
red, on HIGH, as the element heats up).

Plants prefer light in two parts of the spectrum - red and
blue. However, we humans don't see too well in either
color by itself. Red light is used where you want to
be able to see, but won't travel as far so, for instance,
aboard military ships, they shift to red light in places
where hatches (doors) might open to the outside. The red
light won't travel as far and the ship won't be seen
against the dark of night as easily.
Blue light, while it travels much further, washes color
out. Try looking at a zoo display of nocturnal critters
and seeing their colors.. you can't. Try looking at a tank
at night in a dark room that is lit by the new
"Moon Lights" you won't see alot of color, you can't.

Mr Kelvin described this in one of his papers. As you
heat a black object it will pass visually, through
the spectrum from red through redish yellow, to yellow
to white and through white to a blueish white, to blue.

SO, aquarium bulbs range in degrees, Kelvin, between
4000K (the red end) and up to 20,000K and sometimes
higher (the blue end).
For freshwater tanks, 10,000K is about as high as one
would want to go. It can be done, but blue lights will
washout the colors of the plants and the fish. So folks
normally do not use only blue lights such as the Actinic
Blue. Usually, they will use combinations of white and
blue lights.

5,000 degrees Kelvin lights or 5K for short, tend to give
off a "yellowish" light compaired to 6K lights, which are
"whiter" and bulbs that are 10K or 20K tend to be bluer.
The higher bulbs (10,000K and 20,000K) tend to be harder
to actually look at, they are more intense, and harsher
on the eyes.

6700K bulbs give about the best "Color Rendering" for
our eyes, and contain both the red and the blue end of
the spectrum for the plants, AND, the best white light
for our eyes to see the various colors (shades of green,
or red, or brown) for plants, and the best light to see
the colors of the fish.

Wattages... An 18 watt flourscent will be "dimmer" than
a 40 watt flourscent. The Compact Flourscent 18 watt
bulbs are brighter than a straight 18 watt flourscent
bulb because the bulb is "U" shaped or is doubled back
on itself, "concentrating" the light in a given area.
The origional concept still remains, the higher the
wattage, the brighter the bulb, and now you know that
the higher the "temperature" of the bulb the more
"intense" the light will appear to your eyes.

Freshwater tanks will use lights between 5000K and 10,000K.
Salt water tanks, especially those with corals and
invertebrates in it will use 20,000K bulbs.

Lighting in tanks is a subject that a book could be
written about, and, indeed, many articles have been
written about in the various aquatic magazines.

Hope this helps...
Frank


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