for every foot of growth average 1 gallon of soil, those 27 watt cfls your talking about at homedepot are 2700k which is red sprectrum best for flowering but the lumens per watt ratio is pretty shitty unless u ordered like 2 or three of those personally i think this site is great for inexpensive anything for ur garden from lighting to nutz to what ever www.kggardensupply.com best of luck