I currently have a 20 gallon tank with an Oranda & a Ryukin. The filter is a Whisper Power Filter 20.
When I throw out the filter and replace with a new one, obviously the beneficial bacteria that were growing on the filter is gone too. Does that mean the cycle has to start over or are there enough bacterias in the tank to compensate for this "loss"? What about when I rinse out the filter between changes? How does that affect the bacterias?
With my old 5 gallon acrylic tank set up, it had a filter cartridge along with the bio-wheel. The bio-wheel was permanent so I didn't have this concern.

I think you tank will go through a soft cycle process as your tank will have some benifical bacteria on the gravel, plants ornaments etc. The bulk of the good bacteria will be in your filter media and since you have thrown it away, you filter has to re-establish with the good bacteria colony which will take a while. I had a bad case where I changed the media and wash some in tap water and a lot of the nitrifiying bacteria died and ammonia level suddenly shot up. It took more than 2 weeks to re-establish the filter as my tank is bare bottom leaving little bacteria colony in the tank to purify the water.

Just check for the ammonia level to see whether is shoots up in a few days. If not, nothing to wory. Since you only have 2 gf (what size?) in the tank, the bio load will be small and hope this will not cause too much problem with ammonia spikes.

Good Luck and keep us posted. I am interested to know the effects.

I've been told that in an established tank, there is enough growth in the gravel, plants, ornaments, etc that it is not a concern. I guess since you have a bare bottom, maybe there wasn't enough bacteria there to compensate for the loss from the filter being tossed out. In another post, DataGuru told me not to throw the filter out but to rinse it with the old discarded tank water until the tank is fully established. Thanks Ranchu man, I will keep you guys updated. BTW awesome set up you got there! Beautiful fishes too!