I need some advice as to how to keep my above ground pool clean.

I have small black particles that build up at the bottom of my above ground pool on a daily basis.

They are small, black and slimy and easily break up and dissolve if you step on them.

They can be vacuumed away but they always reappear the next day.

I need to know what causes them to form; only then will I be able to permanently deal with them.

Also, I have a thin green slime that builds up on the side of my pool. After a week the slime becomes very noticeable.

What causes the thin green slime to form?

I do add chlorine on a regular basis. Isn't that supposed to prevent slime buildup?