I have an FX underneath one tank and although the openings are big enough to move the filter in and out,thank goodness,it is still a pita to do so in order to clean the thing....I have the FX sitting beside the stand on my other tank.Mine is alot of work due the my cabinet, the doors are too small to pull the filter out, so I have to do all of the work with the canister still under the tank. I really didn't think it through when I put it in through the big openings in the back. One day I'm going to get brave enough to cut the door openings bigger.