you can use a little common sense calculations w/o the need of a
structual engineer
a gallon of water equals about 8 pounds
i have a 75 gallon aquarium w/ a 5'x1' footprint
75gals = ~600 lbs
i figure 3 200 pound men in stand next to one another in a 5'x1' area
w/o the floor caving in
so i'm safe