Filter bio bag

[guppylvr11]

I have a Tetra Whisper 10i filter. It uses bio bags. How often do I change these bio bags? It looks a bit dirty but I don't know if it's time to change it? Also, how do I change it without causing my tank to go through a mini cycle?

 

[UntimelyLord]

It looks to me that those "Tetra Bio Bags" are activated carbon enclosed in a thin filter pad. (This is misleading because it sounds like they should be filled with biological media!) Most tanks don't really need activated carbon; activated carbon can help remove odors and water discoloration but if you keep your tank clean you shouldn't have a problem with that. They can also be used to remove medication from the water after a treatment period.
Personally I would just leave it for the extra beneficial bacteria that is on the filter pad part; after a month or two activated carbon has been depleted. Or you could replace it with an extra filter pad; if you have a filter pad in the filter it should be okay to replace one filter component (the bio bag) without creating a mini cycle because there will still be enough beneficial bacteria in the filter. Just don't do this at the same time as you rinse the current filter pad (in used tank water when you do so).