How often do you change your filter cartrides?

[evanklee55]

I have a regent filter for my 10 gallon tank. How often should i change my filter cartridges? I am wondering.

[blitzen25bm]

not too often, i just rinse mine in old tank water.

[Kagh't]

as a good rule, when a sponge doesn't take back it's form after you squish it within a few seconds (even in water) then it's definatly time to replace.