waterdrop
Enthusiastic "Re-Beginner"
In my opinion the only really good time to switch out media is *before* a fishless cycle, not during it. Once you are in the middle of the process you are stuck with what you chose, unless you want to through away a lot of bacteria and have a potentially big setback.
Although manufacturers and aquarists alike have never-ending discussions about the efficiency of various type of media at performing the different filtration functions, the reality is that most media types perform multiple functions, especially mechanical and biological.
I suspect your sponges contribute a greater percentage of biological filtration to your sytem than those biomax ceramics do. Both those types of media perform both mechanical filtration and biofiltration. The bacteria will attach to virtually every surface they can get at, especially in the wonderful environment inside the filter where they can get the right flow of ammonia and oxygen and minerals. They will be all over your carbon too, so to ease the carbon out of the picture you'll have to wait until the biofilter is much more mature (say 3 or 4 months at least) and then take out small subsets of carbon, replacing it with pieces of fresh media such as sponge or ceramic. In a big 305 though, you'll have lots of other media volume as buffer and the process will be quite easy since there are trays and room to do whatever you want.
~~waterdrop~~
Although manufacturers and aquarists alike have never-ending discussions about the efficiency of various type of media at performing the different filtration functions, the reality is that most media types perform multiple functions, especially mechanical and biological.
I suspect your sponges contribute a greater percentage of biological filtration to your sytem than those biomax ceramics do. Both those types of media perform both mechanical filtration and biofiltration. The bacteria will attach to virtually every surface they can get at, especially in the wonderful environment inside the filter where they can get the right flow of ammonia and oxygen and minerals. They will be all over your carbon too, so to ease the carbon out of the picture you'll have to wait until the biofilter is much more mature (say 3 or 4 months at least) and then take out small subsets of carbon, replacing it with pieces of fresh media such as sponge or ceramic. In a big 305 though, you'll have lots of other media volume as buffer and the process will be quite easy since there are trays and room to do whatever you want.
~~waterdrop~~
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