I have a 55 gallon tank that we are using for cichilds. The tank has been set up for quite a while and has been very stable. I noticed that the tank was not as sparkling clear as usual and fugured that meant it was time for some cleaning but when I started my task I realized that my Fluval 305 filter was barely moving the water in the tank when in the past it has had a very powerful flow. After replacing some of the media in the filter and doing a water change the pressure is just as low as before, where do I start troubleshooting low flow/circulation in my pump? I read the Fluval manual and it has no troubleshooting tips or suggestions, any suggestions will be greatly appreciated.