Carbon :S

[westy101]

I have a spare external filter that I would like to use and was thinking of using something like carbon instead of sponge in one layer ?

 

[westy101]

Or glafoam or ceramic media ?

 

[mr_X]

carbon is good. the ceramic rings are detritus capturing and could possibly be a source of nitrates down the road. they would need regular rinsing, to ensure this doesn't happen.
i would change out carbon monthly.