I've been looking at Odyssea lighting from Aquatraders.com and the prices are very attractive. I am setting up(very slowly) a 60 gallon dirt and STS tank that is 36"x18"x21". I want to go low tech and low to medium light plants. Should I get the 78 watt(2x39w T5HO) or the 156 watt(4x39w T5HO)? I dont want to use CO2. Because it is a deep tank I am not sure if two bulbs will give enough light to the bottom of the tank. Help!