Whats more important Kelvin or Wattage? (lighting for 20gal)

[angelicdeity]

I am getting very mixed messages and need a simple answer.
I have a 20 gallon and 29 gallon tanks both of which i want to be planted.
Both tanks are currently planted with anubias, crypts, carpet swords (i thing), java fern, wysteria, vals and cabomba. On my 20 gallon tank i have a 20W 10000K T12 light, which has a reflector. Everything is growing perfectly, the cabomba is branching off and the anubias is growing like crazy, the other plants are slightly new.

IN my 29 gallon tank, which is a mirabello 100L, came with a built on hood, it has a 12W bulb which came with it, and an 18W bulb (its a double hood, which holds two 18W bulbs). The 18W bulb is 10000K, T8 and with no refelctor. In this tank i am haing problems, i.e plants not looking as good as the other tank.

At my lfs they continuiously tell me its not lack of light, that 10000K is sufficient. From all i have read that is not true, i need wattage rather than K. My mother aggrees with the fish store, and i need proof that this is incorrect.

So what should i do? I am sure i need to upgrade the lighting, but i am not sure how and where to get cheap but sufficient stuff in australia. Also how would i upgrade an build in hood (attached to the tank)?

So to conclude, Is K important or wattage? How to upgrade? thanks guys
Kylie

[GulfCoastAquarian]

Intensity first, then color spectrum. If you're just on the verge of having adequate intensity, them color spectrum can make the difference between growth of plants and growth of algae, but you're still a bit below adequate light intensity levels to worry about Kelvin. Your 10,000K bulbs are most likely providing a great deal of light in the blue areas of the spectrum, which plants can use to grow. They also need wavelengths in the red spectrum, so you definitely are limiting their growth a bit.
On both of your tanks, you're at around 1 watt per gallon. I'd shoot for doubling that. Unless you want to discard your current built-in hood and go with an all-new light strip above your tank, my recommendation is a retrofit kit.
I wish I knew where to look in Australia for your lighting upgrade needs. I know Fulham makes a 220v version of their Workhorse ballasts. They run around $25-$35 here in the US. You could use one of those to run a 55w Power Compact bulb inside your current fixtures.

[Rex Grigg]

Your LFS is smoking crack. It's all about power baby! Watts rule. Once you get the watts then you worry about the color spectrum. That's why there is a rule of thumb called watts per gallon.

[angelicdeity]

Thanks, thats what i thought, i just needed to clarify. Does anyone know where i can get an article or something saying this to show may parents so they don't hit the roof?
Thanks, Kylie

[Rex Grigg]

Well any decent planted aquarium book will show that. Or you could have them come here and read the forums. If you want a I have very basic and in the works primer/FAQ up at http://members.dsl-only.net/~rex/