First, test your water and post your numbers for these tests to the "gurus" here can give you more detailed advice:

Combined Chlorine
Free Chlorine
Total Chlorine
pH
Alkalinity
Calcium Hardness
CYA (cyanuric acid/stabilizer/conditioner)

Your chlorine level needs to be keept at a minimum level according to Ben's Best Guess Chart (depends on the amount of CYA you've got in your pool) until the water clears up. What the pool store told you might be overkill.

27' above ground round? How deep?