Help removing stains at the bottom of the pool

[AmmarDaStar]

Hi I have two kind of stains in my pool, one is the left over leafs that were at the bottom of the pool for a long time and the other is black marks where there is cracks in the pool floor, how/what is the best method to tackle each of them?

Pic included for reference, I hope it's clear

 

[Texas Splash]

When we see stains on the pool surface, we tend to think of residual material that sat on the bottom or metal deposits that were introduced to the water. You may want to try one of the following:
- Some crushed vitamin C tabs in a sock and scrub
- Carefully apply a chlorine tablet and move gently back & forth
- Wire brush

If the black marks from cracks are from some repair work or something in the past, there may not be much you can do, but if you have more details about those cracks let us know.