A 30 gallon rubbermaid is a lot bigger container. More volume plus more surface on top. I have an 18 gallon right now (24x16) on top, while a 30 gallon is (32x19). Think this would help? A 5 gallon bucket has a 12 radius. So, 4 plants in 5 gallon buckets would take up 4 square feet, while this...