I just got a 45g high tank, it's about 24" high without any gravel. I intend to use florrissant lighting. The tanks is 25" wide so after building a canopy I shold be able to use 24" tubes. The tank in 18" deep. 25x18x24 What I am wondering is how many 20w tubes should I shoot for. The tank will be a fairly low tech tank, no CO2 or substrate heating. Any recommedations? Allen