Watts Per Gallon/litre - Any Help?

[minnnt]

The temperature of the bulb. The higher it is the whiter/bluer it will be.

 

[OldMan47]

A typical cool white bulb is yellowish and about 2700K to 3000K, sunlight at noon is around 5500K and fairly white, a 10000K tube has a definite bluish cast to it and looks very harsh. The K rating you use is up to you and your own tastes. Research has shown almost no effect of spectrum on plant growth as long as the spectrum was within the range that the plant could use, which includes any tube from about 2700K to 10000K.

 

[waterdrop]

Totally agree with minnnt, ianho and OM47, less light slower, more light more growth and an excellent summary of K by OM47. One of the most common problems I've seen over the years in the beginner section is just pouring in too much light for whatever reason. This is why I run through the generalization of 1 watt versus 2 watts. It is relatively easy for beginners to remember and apply to different size tanks when thinking about how to get started with these things.

ianho is right of course - once the light is up there and on the timer then there are going to be plenty of other things to think about that will help them to well...

WD