I'd hang on to the dichlor, unless you do a drain and refill. Dichlor adds 9 ppm of stabilizer for every 10 ppm of chlorine.

Instead dose with PLAIN bleach, at the rate of 2 gallons of PLAIN 8% household bleach for each 10k gallons of water in your pool. Even if you're going to drain, you don't want your pool to get totally swampy. Add 2 gallons EACH evening until you drain, or until the algae is all gone.