The human eye can see down to 40 microns, so if you can actually see free floating particles, then those are fairly large and can be cleared with something a little larger than that, say 100 microns as a filter. (It will clog and trap smaller particles over time.) If you can't see the particles, but it "appears" hazy, then the particles could be quite small. Smoke for example can be as small as 1 micron or less but we can see it.
I would also consider a UV filter if you think it could be free floating algae. Otherwise, you need to plan on finer filter sizes than 100 microns. Those are obtainable in smaller sizes, e.g, 25 or 50 microns. As they are used much smaller particles will get trapped between cleanings.