Changing Filters - Bio Vs Mechanical/chemical

[Bruno]

Quick question on changing filter medias. I have seen the question asked  a few times, but am having some difficulty merging the answers together and applying to my filter, so sorry if this is a bit of a repeat question.
 
I have a Marineland Penguin 150 that has a bio wheel as well as a insertable mechanical/chemical filter composed of a rough blue poly fibre and a packet of carbon sandwhiched inside.
 
I know to never replace the bio wheel as that is where my bacteria is supposed to be growing, but I am unclear on how often to replace the other media pack (if ever). I can clean out the poly fibre in aquariium water, but I wasn't sure about the carbon in it since I know it 'wears out'. The maunfactur wants it replaced every 2 to 4 weeks so I keep adding $$$ to thier pockets, but I am concerned about losing the bacteria that must also be growing on that filter besides the biowheel.
 
It has room for 2 of those cartridges, so I can insert a second to start growth before removing the first, but I notice that slowed down the flow just slightly, and was enough to make it harder to get it going again after shutting down the filter for a water change (I leave the biowheel floating in the tank to keep it from drying out, though a water change is quick so that may not be needed)
 
Anyway, any comments that can clear that up would be appreciated as I dont really want to be losing bacteria and spending money if it is not needed.
 
Thanks

 

[fluttermoth]

In theory you should have enough bacteria on the biowheel, and it shouldn't matter if you change the cartridges.
 
However, more room for bacteria is always better and, as you say, the LFS is getting lots of your hard earned pennies, so I would get some normal filter sponge and cut it to fit one of your cartridges (or the space where it lives), then you can leave that one for extra bio media, and just have replaceable floss in the other cartridge slot.

 

[Mikey1]

i would forget about the marineland inserts, here is what i would do....
 
go to your LFS and buy a foam insert for an aquaclear 110/500 filter, it will look like a big brick of foam,
 
cut the foam brick with a sharp knife or scissors into a piece that will fit into your filter,
 
now cut that piece into two halfs,
 
put both the foam halfs into the filter.....when you need to replace the foam in the future (which should not be very often) replace the halfs alternately, never at the same time with a new piece of foam cut off the brick....
 
no need to use carbon,
 
leave your bio wheel alone, it will last forever

 

[Bruno]

Awesome suggestion, thanks