GREAT QUESTION!! I have been asking the same question for the last month and have gotten some interesting answers but I think that I have my own opinion embedded firmly in logic...First of all I am going to get rid of my UGFs and replace them with sponge filters. The UGF has one major flaw and that is that eventually the system will become unstable and you will not like the results that follow. The advantage of a sponge filter over a UGF although not as attractive is you can clean it without breaking down the entire tank. Rick Gomes - -----Original Message----- From: owner-apisto@listbox.com On Behalf Of Robert Marshall Sent: Tuesday, October 28, 1997 5:07 AM To: apisto@majordomo.pobox.com Subject: Under ground filter or not? Should I install an under ground filter. Lots of opinions about no but no reasons why. Leaning towards get one so tell me your experiences. yes or no. If no what filters should I use in addition to my Fluval 4 - tank is a 50 gal. Sand, which I like, or gravel. If I don't use a UGF I am going to insert a layer of peat moss.