Before considering chemicals, you need to determine what is the cause of your murky water.
The first step is to perform a "jar test".
You need two decent-sized jars (preferably glass). Fill each jar about 80% full. Put one in a dark place (closet) and one in good indirect sunlight (like a windowsill that is NOT in full direct sun). Observe both jars for a week.
If both jars clear up in a week, then you probably have a mechanical turbidity issue. There should now be material at the bottom of your jar. Some organisms in the pond are stirring up sediment or debris to make the water murky. I could even be humans, dogs, etc. as the organisms.
If the jar in the dark clears up in a week, but the one in the light stays murky or colored, then your murky water is probably due to a phytoplankton bloom. The photosynthesizing organisms died in the dark.
If both jars stay murky for at least a week, then you probably have suspended clay particles causing the murky water, and you will need to treat the water to change the ionic balance.
The solution for each problem is different!
Unless you added a lot of clay on top of your liner, then I suspect your murky water is probably due to plankton blooms. (But you need to find out for sure!)
Below is a good link about that topic.
Plankton Blooms[Much of that "jar test" advice above is from an old post by teehjaeh57.]
