Okay, so the media isnt the problem. Next step is to clean the impeller. Turn the filter off, take the two top covers off, and pull up on the black plastic intake tube. If you are facing the filter, it's on the right side, and kind of an upside down "U" shape. Most likely, all the pieces will come up together. but there should be what looks like a plate on the inside end. The impeller fits into the bottom of the plate and is a black grey cylinder with metal shaft though it and a yellow set of fan blades on it. Pull everything apart and wash it all off. Often times, algae will build up both in the tubing and on the impeller. This chokes the water flow, and you should wash it out every few months. Also, on the re-install, there is a little arm with a tab on it that comes off the plate. The tab locks into a slot on the right side of the inner wall. You will see it when you take it out.