02-25-2013, 04:17 PM
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That looks the same, but it may not be, though they do call it ceramic. I'll explain.
In the Eheim and Rena canisters (and Fluval, probably others as well) the first media through which the water passes is ceramic disks or circles. The intent is simply to trap the larger stuff so the later media and pads don't get clogged as fast. Eheim calls this Ehfimech, Fluval calls it Pre-Filter, I can't remember Rena's name for the same thing. They all say this never needs replacing, you just rinse it off.
The second media is the "biological" stuff, Eheim calls it Ehfisubstrat, Fluval calls it BioMax, can't remember Rena again. Technically speaking with plants you don't need this, but the basket is there, so I fill it. They all recommend replacing this, I never have in 15 years, just rinse it.