FishProfiles.com Message Forums

Some people say that 6700k is best...some people say that 18,000k is better than 6700k... What's the best?

I'm asking because I have one lightstrip on my 29g...it takes an 18 watt bulb. I've read that even with like 0.6 WPG, medium-high light plants can grow with 18,000k+...and I'm trying to get out of doing a DIY setup...I just want to get a high temp bulb...

Waddaya think?

I know i go for high temperature bulbs rather than watts, since i use liters instead of gallons and i'm both bad and lazy at doing conversions so my tank has 2 light stripes 20W but 10,000K each, and i'm growing high light plants.

Some people also say spectrum is not so important - intensity is the key.

But where you will see a big difference in color temps is how the tanks look to the eye. An 18000k light will make your tank look very blue and wash out the colors of both fish and plants. 6700k is widely chosen because it's a temp that is both suitable for plant growth and bringing out the best colors in both fish and plants, a win-win. Higher temp bulbs can help if the tank is deep, easy for the light to penetrate to the bottom. Like Falstaff I also use 10,000K bulbs (2ft deep tank) and am quite happy with them. But really you can't go wrong with the 6700K.

In short a higher temp bulb will do nothing for increasing plant growth, sorry but no way to to get around intensity.
What may help is using a tri-phosphor bulb, a bit more expensive (but still probably cheaper then a 18000k marine bulb) but they are up to 20% more intensive then normal flourescents. Lumens much more important then color temp.

---

Some days you're the pigeon and some days you're the statue.

Remember that age and treachery will always triumph over youth and ability.

Hi,
In the end, it is entirely up to you, and how your eyes
view your tank.

This site will show you what a tank looks like when
lit by various bulbs...check it out!

http://www.aqua-web.org/users/saurama/index.htm

Freshwater plants prefer a spike in the Red and Blue
parts of the spectrum. Bulbs in the lower temp range
4-5000K cast a yellowish glow and seem to some to be
"dim." Colors are understandably faded, and the tank
has a yellowish tinge to everything.
Bulbs in the high end (10,000K and higher) are at the
blue end of the spectrum. We tend to preceive them
as brighter, and these bulbs give off a bluish light
that tends to washout colors.

Bulbs 10,000K and higher are specifically for use in
Saltwater tanks that house corals and invertebrates.
This intense light is used by these creatures to
create algae, and for other reactions and chemicals
that produce their intense color as well as food.

Blue light penetrates deepest into the water where
reds are scattered and absorbed within the first
couple of feet.

Light around 6000K - 8000K tends to allow humans to
see greens that are green and reds that are truely
red. You can obtain flourscent bulbs at 6700K or
8000K.

In many cases hydroponic farms use lights above
10,000K.

It's up to the viewer what they preceive when they
look at the tank. And, it's up the the viewer how
much they want to shell out for a bulb. Ordinary
6700K bulbs can be obtained easily, at the local
hardware store - Bulbs labled SUNLIGHT or DAYLIGHT
are 6700K bulbs. The others are considered
"specialized" bulbs and cost far more.

Frank

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

I think your time and money is best spent sticking with 6700k for the color temp, and either retrofitting your hood (check out http://www.ahsupply.com ), or getting a new fixture altogether that holds compact tubes, enough to get to 2 or 3 watts per gallon.