planted tank/lighting please help!

[MediBedi]

I'm trying to setup a grow out tank for my plants so I could use them for my future fry tank.. So far I got the substrate I need. Next is the lighting.. What do I even look for? wattage or lumens?
I found a t5 3ft double bulb light fixture that holds two 21 watt bulbs and I "think" around 3500k lumens each, would that work? Its not an aquarium light fixture but was wondering if it'd work?
Going to be using it on a 20gallon long tank
Just don't want to spend an arm and a leg... looking for the cheapest way to go lol...

[Oldfishlady]

The light bulbs I like to use over all my natural planted tanks-I get in the lighting dept at either wal mart, home depot or lowes since they are much cheaper than aquarium bulbs-especially since you need to change out florescent light bulbs every 6-12mo due to color temp loss.

I get the GE "Daylight" 6500k florescent bulbs-the watts vary based on length-anywhere from 20-40w on most of my tanks.

Your color temp is what is important for growing plants-The kelvin between 5000k-7000k-with 6500k being ideal and close to the color temp of the sun.