Pool liners can get a little slimy feeling, or mildewy around the top. But they are also somewhat fragile and you shouldn't use harsh cleansers that can break dow the liner material. This leaves either purchasing a special cleaner or choosing a gentle home remedy that won't damage the liner but will still leave it clean, and mildew free.
Vinegar and Baking Soda Cleaner
Mix vinegar, baking soda and hot water in a bucket. Use a mop to clean the liner. This will kill mold and mildew and leave the liner clean and fresh smelling.
Dissolve powdered dishwasher detergent in a bucket of hot water. This detergent is made to be gentle enough for dishes, but tough enough to cut through pool liner mildew and dirt.
Baking Soda Paste
Mix baking soda with a small amount of hot water to make a thick paste. Apply with a sponge or sponge mop to lift away all dirt, stains and mildew before rinsing clean.
Basic over the counter vitamin C tablets can be dissolved in a small amount of water and applied with a spong or sponge mop to remove stubborn stains as well as basic dirt and mildew.
Mixing a bucket of 1 part bleach to 5 parts water will clean the pool liner without causing the vinyl to break down.