Indoor container size

[The Full Auto]

I got the 20 gallon tubs today and also I am at week 2 for the super soil mix. How much of the super soil shoud I put in the tub? Bottom 1/3 ? I will be putting 4 autos in each tub, 4 tubs makes 16. These are under a 1000 hid in a 4 x 4 room. Little to none on the watering huh? I like the sound of that.

lol no man probly not i planted 5 autos in a trash bin that was probly 40 gal i watered it twice the hole grow was great probly only had to water once but i had raped the bin wit reptile heating pad which dont give alot of heat but keep the soil warm had great grow and lookin to do it again since the winter weather has arrived ( only really grow in fall and winter cus of heat issues in summer)