If you go to lowes or home depot you may be able to find finely ground dolomite sand which is calcium based with a little extra magnesium. I used it on my 150 gallon build and it worked out real well.
Drs. Foster and Smith offer good shipping rates. I ordered 300# of sand when I moved to montgomery and paid $17.99 for shipping. If looking for quantity, that may be a cheap-ish option.
