I assume that you're going to use the 2 tubs like Bodom did as one unit, so I'd say 1-2 full grown flowered plants in there. 30 gallons are the smaller ones, I used 1 52 galloner and fit 3 comfortably in it, had 5 in there once, was just craziness, but worked out.

A 15inch fan eh? on a 30 gallon tub? Does it take up the entire top of it? haha:stoned: Painting the inside is a smart choice, flat white of course. I used foil tape, which seemed to work well also.

I use Fox farms, Ocean forest soil. Expensive, but I have never failed using it. I add perlite to it, probably 10-15% perlite, the rest Fox farms. I use this mixture from start to finish. Might be a little "hot" for seedlings, but once again, never failed using it.

A note about smell. Marijuana, while growing (and any other time really) smells, even in a laundry room in the basement. My ladies always perfumed my ENTIRE place. Hopefully smell isn't an issue for ya!:stoned: