Yes, I agree with JW, Colleen take a pic of your pre filter. Also, did you say your pump is out of the water, with a line in that you pull from? All of my pumps are submersed. The one that was going slower was an older pump that I am using as the bubbler on the goldfish pond, and it go going so slow that the hard cold snap froze the pond. Two days later the whole pond was thawed out ... that's how we roll in IL! 10 degrees one day, 55 two days later. LOL It had a filter sponge thingy in the "cage" where the water pulls in. I don't have any type of line just let the water pull through. I probably should have just taken the sponge off, as the water is simply pulling in on one side, pushing out the top of the pump to make the bubbler. As long as it's not large leaves that might clog it, most everything small will go through. My bigger pumps (4200 gph) are Laguna Max Flows. Same thing, but no sponge under the cage, as those can push pretty good sized stuff through them. Never have had to clean them off but maybe once a year, but the one in the koi pond is the one that failed to keep the waterfall running, so I'm not sure yet what is going on with that.
So, when you get thawed out there, Colleen, show us some pics of your pre-filter. Thanks!!!