I use to have 2 hob bio filters on my 55. What I would do is; The filter on the left would get fresh filters, I would take the old filters out of there and rinse them out in salt water then place them in the filter to the right. The ones from the right filter would get thrown away. I did this every 2 weeks according to the manufacture recomendation.
I NEVER DISTURBED THE BIO MESH, just changed out the carbon filter pads. HTH