I was looking for a cheaper alternative for lighting a planted tank, and after looking through some posts here and on the planted tank forum I came across cfl bulbs. 23-26 watt bulbs seemed to work. The only place around here that carried cfl bulbs was a tractor supply and they only had two types. I bought the daylight bulb and its 6500k with 40 watts. Will this work for a 20 gallon tall with amazon swords? My 29 gallon produced so many runners I need to move them to my "no light" tanks and I just don't have the kind of money right now to upgrade the lights to the real deal.