hi, i just recently learned i need some cal mag, but im having trouble finding where to buy it. Is this something that can be bought locally, like at lowes? Or is there something i can use as a substitute that i can buy locally? If not, does anyone no of a good website thats cheap lol. Im always on a budget, and i think i just need a small ammount, not like a gallon, that just sounds expensive. Thnx for all the help every1!