Ok, I am doing a little math to figure out I am not that good at Math btw) so let's see if this makes sense
According to this
http://www.tpic.ca/3_specified_loads.pdf, our home floor live load is 1.9 Kpa which is around 40 pounds per square foot.
Your tank is 72x20 so roughly 12 sq ft in total.
Now calculate how many pounds of your tank:
a full water of 150 gallon is approx 1224 lbs
+ 280 lbs (sum) + 100 lbs (stand + equipment)
so that is around 1604 lbs
so 1604 lbs over 12 sqft is 133 lbs per sqft. So you are 83 lbs over per sqft
I am probably wrong here lol
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Clk-Class