once a month depending on how much and often you feed them

Good question. Your filter should be claned roughly every two months, however it depends on how dirty it gets. I don’t need to clean mine but once every 4-6 months with water changes every 4. Since salt tanks are not like fresh water waterchanges are not always needed once a week or once a month, since it goes by your water quality not routine maintenance. If you see the excess brine shrimp “clogging” up the works or laying around on the bottom of the tank, you may want to do a change or atleast a partial cleaning.

Again it just depends on YOUR particular tank since each and everyone is different. I have bristle worms so I have very little to no excess foods in the tank. They do a bang up job on the cleaning side.

A Fluval is time consuming to clean. Here’s what I do. I put a Hydro-Sponge filter on the intake pipe of my Fluvals,as a pre-filter.I clean the pre-filter sponge every other water change. The sponge inside the canister never gets dirty(well almost never) and it acts solely as a growth medium for Nitrifying bacteria. The out-fall of the spray-bar tells me when the pre-filter needs cleaning and you don’t risk the health of your bacteria colonies by removing the canister sponge.

You should be doing partial water changes (NOT total water changes) once a week or at least once every other week.
If you use filter media that gets depleted, such as activated carbon, it needs to be changed once a month. Your filters should be OK as long as you keep them clean. Only rinse them in a bucket that has aquarium water which you are taking out, don’t rinse it in the sink otherwise you risk destroying all the beneficial bacteria that live on it.

I would think that you should clean the filters soon. Only clean filters work properly. Also, your water should be changed around twice a month.