I had a guy come in to the lfs I work part time at and he asked me how we keep the display tank so clean. I replied its not that clean, not that very dirty just had some algie on the glass, and he said it was clean comparied to his. I then asked about his water, if he was running carbon or gfo and he said no just a skimmer and only a skimmer on a 55gal tank. No filter or any thing just a skimmer and lights. He said he was told thats all he needed on a tank that size, by the pet store in town that he shops at. I explained yes you do and I don't care if you buy it from here or not, get a damn filter even if its the hang off the back kind. He did go buy one... from some where else that is a cheaper model than the one we have, but at least he has a filter now.