crushed lava rock for filterless tank?
I'll be attempting a filterless tank for some shrimp pretty soon and I've been thinking of ways to increase the surface area for bacteria. Would it be helpful at all to add a layer of crushed lava rock as the bottom layer of the substrate? Or maybe even as the top layer? Would crushed lava rock + crushed ceramic ring pieces be even better as a sort of boost to the natural biofilter? However, if they are on the top layer of the substrate, would detritus and mulm get clogged up in it too quickly and just become a mess?