What is the difference between....

[kcinimod]

Eheim Ehfimech, Bio-Glass, ceramic rings and fluval's Bio-max??

Eheim's Ehfimech is the cheapest by the liter.. I can't tell much from the pictures on the Dr's catalog - except that they're all round and hollow. By the name though, i'll assume Eheim's Ehfimech is for Mechanical filtration and others for Biological.. Would that assumption be correct? Would I need both??

I'm using 2 Rena XP3's on a 125.. Want to go with something in the middle basket that'll work.. cheaply..

 

[SMS]

Your assumption is correct.
Something cheap that will work is Eheims ehfiLav, small pieces of lava rock that is rather pourous.
Since the bio media will last awhile I would go with something better like Strat, Matrix, or biomax.