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ok from the posts i have read and questions i have asked. i gather that i want a 6,500k - 10,000k bulb. but at the stores and places online the plant bulbs are 2,500-4100. i dont understand why they say for planted tanks when people say that the others are better?

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Its an industry underestimation thing. While its perfectly possible to grow many plants under the lower K bulbs, the real pros use much higher wattages. Its probably just an averages thing, the manufacturers try to produce bulbs that arent so bright that they cause an algae explosion for people whos water quality might not be tip top, and they try to use frequency of light to encourage growth. For low light plants this is fine, but coinnosseurs have to find bulbs of much higher brightness, and sometimes use co2 for healthy growth, none of which is truly necessary for most people.

I have all my tanks festooned with loads of plants with lots of healthy growth, but Ive never as yet bothered with higher wattages. You can do it without, its just a perfectionists thing.Besides, many fish are seriously annoyed by lights that are too bright, and I keep quite a few of them.

There are quite a few ways you can successfully grow plants, high lights, lowlights, ferts, co2, its all doable, there is no one way.

Hi,
Plants use the light in the red and blue ends of the
spectrum.

The K rating of a bulb is derived from heating
a black iron object. Think of an electric stove with
black heating elements, or better yet, a piece of black
iron heated by a welding torch.
In each case as the temperature of the iron is raised
the iron becomes first red, then reddish yellow, then
brighter yellow shifting to white, then a glaring white
shifting to blue. The temperature of these color shifts
are measured in Degrees Kelvin, or "K". A bulb at the
red end of the spectrum have a lower temperature than
those at the blue end. What is being said is that the
light being given off is the same "shade" or "color" as
that black iron object would be at that temperature in
Degrees Kelvin.

Theoretically, you could put a red bulb and a blue bulb
over a tank and grow plants. If you did, I'd use
fluorescent bulbs in the experiment. BUT, you would not
be able to see the colors of the fish and plants.
Red light is used aboard ship after dark because it
allows you to see and work, but is dim enough that when
you step outside into the dark of night your eyes more
rapidly adjust to the darkness. Red light is used in zoo
displays to allow you to watch nocturnal animals going
about their business during our periods of daytime.
Using a blue light washes out the colors (such as moon
lights) and things become shades of grey.
The spectrum in between the two extremes is where we see
color and where you would want to choose your aquarium
bulbs.. You would want to choose the Daylight part of
the spectrum, one that contains all of the colors and is
a "white" light.

Here is a site that describes a bit more graphically, the
Kelvin rating for bulbs:
http://www.1000bulbs.com/page.php?s=KelvinTempExplained

Note that as the temperature climbs, the light shades from
"yellow" through white to blue.

I prefer to use bulbs on my planted tanks that are
6700K and a max of 8800K. Bulbs as high as 10,000K are
used in freshwater tanks, but once one gets over 10,000K
the light becomes BLUE such as the Actinic Blue bulb and
when those are used, they are combined with a lower K
rating bulb to modify the result making the overall light
more like daylight. Bulbs over 10,000K are used in salt
water tanks, especially reef tanks and tanks containing
invertebrates.

This is another site with more detail that compares lights:
http://www.aquabotanic.com/lightcompare.htm

Generally speaking, as a rule, terrestrial plant bulbs
give off a pink or purplish glow that (IMO) I find quite
objectionable. Low K rating bulbs make the water yellowish
and dim, while very high rate bulbs 10,000+ are simply too
bright, and harsh. I prefer bulbs around 6700K-8800k for
my tanks. The light is white, and photos look great.

Frank

-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

thanks guys. on my 29gal i have a corlife dual fixture coming in at 42w total. one lamp is 6700k and the other is a colormax "full spectrum". does the full spectrum mean that would help the plant growth? and i also have the hood light that came with the tank, what should i replace it with?

and one more ? what would you recommend for a 10 gal. i have a 18" fixture with no bulb right now. im looking for one to put in it. i want to put some java moss and some micro swords

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Hi,
Yes, the full spectrum bulb will be fine with plants.
"on my 29gal i have a corlife dual fixture coming in at 42w total......i also have the hood light that came with the tank, what should i replace it with?"
I'm confused ... Doesn't the first part say what you
are replacing the hood that came with the tank with?

As far as the 10G tank is concerned you are, in a sense,
mixing plants of different light needs. The moss will grow
with just about any light (wpg) while the micro swords will
require around 3 wpg. In a 10G tank you might get away
with using 2+ wpg but it will be up to the plants and the
bulbs you use.

Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

thanks frank. just to clarify i have the light that came with the hood(original bulb). and a corlife with one 6700k and full spectrum

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