Sorry I've been silent recently. Underwent a follow up monthly treatment that put me out of commission for a few days, and now I have some family visiting from out of town. So I will be checking in daily but I'm afraid I won't be as active over the next few days.
My lid is finished and the tank is painted!
As you may recall I tossed the old filter media when I cleaned up the tank. It gives me a chance to reinvent my filter
I decided to not get the same Eheim media that originally came with the filter. I also decided to put the biomedia as the
last step in the filter (Eheim puts it as the next-to-last step, before the polishing pad). I figured you want the water as clean as possible before it hits the biomedia to avoid clogging the biomedia pores as much as possible. Eheim doesn't do that because putting their polishing pad under the ceramic biomedia would squash the polishing pad (which looks a lot like polyester batting).
So I'm starting with Eheim mechanical ceramic media at the bottom (I had some left over) as a first very coarse mechanical filter. Then 3 successive layers of sponge from coarse to fine, then a polishing pad, and then the biomedia on top. To avoid having the sponges and polishing pad squished by the ceramic biomedia I will use poret foam, because it's supposed to be non-compressible (it's the same foam Eheim uses to make its blue coarse sponges). And instead of using "squishable" polyester batting I will use a felt pad as a polishing pad.
Instead of using Eheim biomedia I've decided to give Biohome media a try. It's made from the same sintered glass used by Eheim but it's supposed to have a lot more porosity and space for bacteria -- including anaerobic bacteria that allegedly turns nitrate into soluble nitrogen. Im not sure it really works, and it's supposed to take months for anaerobic bacteria to get established, but if it does it should (in theory) help keep nitrates close to zero. We'll see.
The Eheim canister I have has some extra space at the top of the media basket. I have always figured it was for temporary chemical filtration (e.g. using a carbon pad to remove medication from the tank) so I've never used it for anything, and it was just wasted space. So I will probably fill it with some polyester batting just to avoid leaving it empty. Extra filtration can't hurt.