It depends on the size and capacity of the filter, the tank volume and the fish load. But I often think that cleaning a filter once a month is a habit that will handle most variations of those things. Yes, its very important to clean a filter, and yes, its also important to know what you're doing so you don't kill the beneficial bacteria. As you know, you want your cleaning operations to take place in a bucket of tank water, not in tap water. If your filter is very "young" (ie. its not been long since you cycled it) then the operations need to be even more gentle. What you do is switch it off and do whatever it takes to transport the filter, with tank water inside it and without getting your cabinet and floors wet, to a bathtub or utility sink where you can work on it. You also take a bucket of tank water there (filter cleaning is almost always done in the middle of a water change.) If necessary you open the filter. For sponges, you gently squeeze (well, after they are very mature, like over a couple years old, you can wring them out pretty hard) them in tank water a couple times to get most of the debris out. You don't clean them in any other way. If your media is in removable trays, you lift them out and dunk them in the tank water and swish them gently around, again to get the debris out. Use common sense to apply this general approach to your media situation. Ideally at the end you can quickly refill the filter box with some different clean tank water after pouring the debris laden water out of the filter box. Then you take the whole thing back and get it going again once your intake tube is covered in tank water at its intake. With some very large cannister filters you can go much longer between cleanings than a month. With some very small filters, you will need to clean more often. If the flow rate out your spraybar seems to slow significantly then this is a typical sign that your filter needs a clean sooner than you thought.
~~waterdrop~~
