Algae growth is determined by a number of factors including the concentration of preventative chemicals, sunlight, air temperature and the length of time that the pool is closed.
For example, a pool closed just after Labor Day runs a greater risk of reduced chemical concentrations (and protection) than one which remained open until Thanksgiving.
The best way to prevent visible algae growth is to physically inspect the pool early in the spring, especially after a warm period (air temperature of 60 degrees or more). This can be done by simply unhooking a corner section (It is not necessary to remove the entire cover). If you suspect that algae is beginning to develop, add the appropriate chemicals at that time and reattach the cover.
You may need to repeat this procedure depending on weather conditions and the time remaining before the pool is finally opened.
If the pool will not be opened until late spring, you may want to hook up the equipment 30-60 days prior to opening your and run it several hours per week to create circulation which will also enhance the distribution of any algaecide.
During this time be sure to maintain frequent inspections since warmer weather may accelerate the depletion of algaecide chemicals.