How much salt does a pond need?
Salt in a pond is measured in parts per thousand. A gallon of water weighs about 8.34 pounds, so raising a thousand gallons by 1 part per thousand takes about 8.34 pounds of salt.
For a pond of 1,717 gallons with no salt in it, reaching 1 part per thousand takes 14.3 pounds, a little over a third of a 40 pound bag.
Why the volume matters
The dose is only as good as the gallons. Dose a 1,700 gallon pond as if it held 2,500 and it ends up nearly 50 percent saltier than you meant. The PondTools salt calculator starts from the measured volume and subtracts any salt already in the water.