Answer:

Get as much of the debris and algae as you can out manualy, you may need to scrub the walls and floors to destroy stubborn algae and other growth. You can also vacuum, but make sure you vacuum to waste so it does not recirculate it back into the pool. The next step will be to balance the water in the following order 1. hardness 2. total alkalinity 3. pH. Once the balance is acheived, you would need to add a metal removing agent if there is any metal typically present in your source water before you add chlorine as once you add chlorine, the metals may oxidize causing further cloudy water and staining. Then you are ready to add chlorine, following the dosage chart provided on the chemicals. You will need to shock the pool first to establish a chlorine level, then keep it going with whatever chlorine you will use. Again, test and balance to make sure you have acheived the proper levels. Then if cloudy water or dirty walls persist, you may want to consider the addition of a clarifier or algaecide. Certainly do use an algaecide if you are sure there is alage.