Hi, and welcome to the forum!!

The stuff you see on the bottom of the pool could be pollen, dirt, algae, or any number of things, but without some more information, it is really impossible for us to tell you for sure.

Can you please post test results (preferably with a drop-based kit, no strips) for Cl, pH, TA, and CYA? Also, what you're using to chlorinate with,(not just "shock" but actual ingredients), any other chems you've put into the pool, what type of filter you have, and whether or not you filled with well water? With this information, it will be easier for us to try to help you solve the problem.

Janet