While I do not have an in-ground pool, I have looked after one and currently have an above ground pool. To close it, I elevate the chlorine levels to about 10 ppm, adjust the pH levels to between 7.2 - 7.6 and cover the pool with a solid opaque and leak-proof cover; All I get in my pool over the winter is a little dust, no algae and the water is clean, just turn the pump on and do a light vacuum in the spring; the cover is the most important contributor to my success, no need for algecide. For an in-ground pool, getting the water off the cover will be a little more work, but it is worth it.