I just installed the eheim classic on my 20 long. I kinda feel for me at least that its easier to clean than my fluval 407.
I disconnect it, and flip it upside down into a stainless steel bowl squeeze out the sponge, empty the water in the bowl, swish it around in some tap water (well water) put the media back in and put some filter floss on the top. Fill it with water and slap the top back on.
I was really impressed with how easy it was to clean