Yeah but there is going to be a massive imbalance in the quantity of those two types of sand. I bet the sand required for aquariums is a rounding error on the amount of sand required for concrete.
Especially as many aquarium owners, these days, use a topsoil-clay mixture instead. Planted tanks take far less maintenance, need less filtering, can fit more (and happier) fish, and the plants grow better in soil.
Yes, though the difference in value is probably not quite as stark as the difference in mass. (Ie aquarium sand is probably more expensive than concrete sand.)
Well not really Bermuda has population of 60000 only so the sand they import for construction might even be less than the sand US import from Bermuda for its aquariums