[JonandJo]

I've just bought a fluval 103 now I need to put the right media in it.

Now my understanding was through mechanical filters first then carbon then biological. However the manual suggests pre filter first which looks to me like a biological filter, then your carbon and finally through a filter pad.

I also know they make unit specific foam pads, but I'm also guessing you'd pay over the odds. Can any filter foam be used just cut to shape.

 

[rickey]

I almost always customize the filter media to my needs. so yes you can use any filter foam cut to fit.
R

 

[Agent13]

And you don't *need* the carbon ... Unless you just want it.

 

[JonandJo]

It was more the order of filtration I was confused at. My thoughts ran along the lines of filter foam first to remove big particles(mechanical), then if you wanted to clean the water up your carbon(chemical) and finally the ceramics to add the bacteria back into the water(biological).

The way the manual says is biological, chemical then mechanical.

 

[Ogre44]

The pre-filter is suggested in order to strain out larger particulates so they don't clog up your filter, so it is mechanical in intent even though it will also contribute to biological (all of your filter media will end up with bacteria on it so it's all bio really).
You have the order correct, mechanical then chemical (if you're going to use any) then biological.