If you have a skippie filter you shouldn't have to touch it. I have had my skippie filter running since Oct 2010 and haven't touched it in 4 years. This year curiosity got the better of me and I decided to pull everything apart so I can see what was in it .. regrettable it cost me a lot of time and effort when I really didn't need to touch it. There was some dirt looks like like a few hands of mud, other than that could of been left as is and it self maintains and doesn't ever needs to be cleaned out as per the skippie filter website. They truly do look after themselves.

if you don't have a skippie filter, I suggest you build one and leave it alone indefinitely.

Here is a link that might be useful: Skippie Filter Homepage