Marine pure, Sera Siporax, etc are all good biomedia, and considered more efficient (less space more bacteria) hosts than "regular live rock". Be it dead/bleached aragonite or "live rock" aragonite.
I'm a fan of Seachem Pond Matrix, which is as good as anything out there and can be found fairly cheap (because its not marked up for salt water market). I think i paid $27 for the 4L bucket, which easily supports 100gal reef with a high bio-load.
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I put it in a "vegetable bag" in the sump, and when I do water changes I "bob the bag up and down" like a tea bag to clean off the media and then siphon out detritus. Works great!
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Side note: When I started this tank I made the mistake of reusing the sandbed out of a FOWLR and the nitrates were "off the scale" high (probably around 200ppm!). With some bottle bacteria and pond matrix it was way down within a 4 to 6 weeks...and now, even with an "overloaded tank" I struggle to have enough nitrates! Probably have too much of it in my sump LOL
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