So I recently moved my 2nd filter (Whisper 60) off my tank to run as a sole filter on my sons 29 gallon. My question is before I never worried much about changing the media on it since it was a 2nd filter, but I started thinking today when I go to change the biobags (holds 2) should I change one at a time or both at the same time? It does have the add on sponges on it.