Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
What are the dimensions?
Length x width x depth (measured in inches) = cubic inches.
Now divide by 1728 to get cubic feet.
Most rocks, sand and gravel run pretty close to 100 lbs per cubic foot.
Garden soil that is mostly sand/silt/clay will be just about that, too. A bit less if it has a lot of compost in it.
Soil Master Select and more organic material products (Potting mixes and soil conditioners) are about half that.
You want to avoid too much organic matter, compost and such in a potting soil. Perhaps look for something labeled topsoil, but read the label CAREFULLY. Copy it and post the list here for more input.
Soil from the garden can work, but it is a specialty sort of project to set that up. Cheap, though!