Pool pump rattles loudly and stuff always floating on pool water, what is going on?

My solar isn't heating the pool. The little stuff on the pool never seems to get to the skimmer to be filtered even after days of 9.5 hours of the pump running on a 20K gal pool. The pool pump rattles like little pieces are in it. Yet, water chemistry is good. No algae. I even took the water to be tested a Leslies and they said it was textbook. At first I was thinking the pump wasn't working yet the pressure seems normal as well. I know we never had this problems with all these little things floating remaining in the pool until I use the net. Please any advise would really help. Thank you so much!