I would agree with Jan. By the time you open in the spring things could have changed a great deal and it won't affect algae growth over the winter anyway.

Normally, we MIGHT (emphasis on "might") worry about scaling but your winterization will have the water away from any metal so that won't be a problem either. Save the acid and effort for the spring. Besides, being a little high on the pH at closing isn't a bad thing as acid rain tends to lower pH over the winter anyway.