well for you if you have a 48 inch or even a 36 inch on,it might cost about 200-400 dollars. Depends on where you get the salt water.
How much salt should be added to hard water depends on what you want to accomplish by adding the salt.
There is no true measurement for lbs. of live rock to gallons of water. The rule usually states 1lbs per gallon but that can be too much. You do not want to displace too much water.
8.556 pounds
The average ocean or sea has a salinity of about 3.5%. In metric, about 35 grams per liter.
A gallon of water per person per day
Tap water does not cost very much per gallon in Michigan. You can purchase it in grocery stores under $3 per gallon.
1 gallon
Salt water is at it's lowest freezing point at a 23.3% salt-to-water solution. This works out to 2.28 lbs. of salt per gallon of water. Source: http://www.varitech-industries.com/pdfs/Salt%20Brine%20Statistics%20and%20Rock%20Salt.pdf
Most chlorine generators require a salt content in the water of a pool 2500 to 6000 ppm
Approximately 7.231 pounds The bulk density of table salt is 1.154 g/cm3. (http://en.wikipedia.org/wiki/Salt) One gallon is approximately 3785 cubic centimeters. Weight = Volume/Density=3785/1.154=3280. g [to four significant figures] There 453.6g per pound. So 3280.g=3280/453.6=7.231 pounds
A gallon of water per person per day
About 8.35 pounds per US gallon.