Sponge filter know how

[TomO]

I’m running 2 large sponge filters in my 75, 1 large sponge filter in my 55 and 1 medium sponge filter in my 29. All have air stones. My question is, how do I know it’s time to clean the filters? My tanks are heavily planted and crystal clear.

[Fish Folk]

If you can visually see buildup of mold, detritus, etc on the sponge surface that is discoloring it, clean it out. Every two weeks, squeeze it out. We like to get a couple pails of tank water to squeeze it in, but some people claim no problems with squeezing out under tap water. Cory posted a demo video on cleaning out sponge filters recently: 

 

 

[Brian]

They are pretty cheap to purchase and operate.  Some people will use two.  Cleaning one every week while cleaning glass, changing water and doing regular tank maintenance.  And then the following week clean the other one.  Either using tap water or tank water.  
Also the benefits of having extra sponge filters that are cycled.  
01.  Sick fish and need a QT tank you have the filter.

02.  That impulse purchase and need another tank.

03.  Another of your tank crashes.

04. A friend needs a cycled filter.   
 

and so on.