I just purchased a 20 long tank from Petco and 40 pounds of co-complete. I'll be painting the back of the tank black and putting a two bulb T5 light on it. I want to make this my primary grow tank so that I can get fast and healthy little baby plants for transplanting in my other tanks. I have a paintball CO2 system and I am wonder what, if anything, I should put under the soil, in the soil, on the soil, or in the water to help me see the best results.