Bio Filter Cleaning?

Question
Ma'am

We moved into a house ~1 1/2 years ago that had a poor 150-gal saltwater aquarium.  Due to the fact that it wasn't set up correctly (no refugium!) and we had zero experience we immediately converted it to freshwater.  The plumbing is homebuilt; one canister holds a mechanical filter and the other we're using as a bio filter.  Per the local aquarium's recommendation we packed ceramic beads and 'grass' into the bio canister which has worked well for the past 1 1/2 years.  The advice we were given was that this ceramic stuff should never need to be changed out; however, my pump has been struggling recently and the circulation has slowed down to a trickle.  I've eliminated clogged intakes, mechanical filter, and everything else as a culprit to the slow circulation, but I'm wary of opening the bio canister as I know it can throw off the water chemistry (and we have about 90 small fish in the aquarium).  Does the bio filter actually need to be changed?  If so, do you have any advice for the procedure?  Appreciate any help you can provide.

Answer
Dear Dave,
The best way to maintain Biological filter media if it becomes clogged, you can use aquarium water in a fish-safe bucket or another container to gently dislodge some of the material to improve water flow. You wont ever really have to replace it. What you need to pay the most attention to is make sure the water flow is going sufficiently through the bio-media and make sure the other filter functions (mechanical and chemical) are working properly and are cleaned (in aquarium water) on a regular basis. How often they are cleaned is best judged by your own aquarium and situation. For example, if once a month filter cleanings isn't working and the filter media is severely clogged. Try doing it twice a month.

Best of luck with your big aquarium!!!
Karen~