Ok, the thread I started on California Blackworms got me thinking about the sand bed in my tank. It's three inches deep, and has planaria, cali blackworms, and MTS for critters and it's a planted tank with plenty of roots, extending usually 1.5 to 2 inches in depth. My tank water never goes above 10ppm NO3 even though I almost never do water changes. Also, the NH3/NH4 and NO2 levels are consistently zero. All this despite the woefully inadequate filter I chose to replace the B9's stock filter with. So, I believe deep sand beds can and do work in freshwater aquaria. I thought, since I'm suddenly in a slump for inspiration for the blackworms thread, why not put something up to do with FWDSB? (Freshwater Deep Sand Beds) My experience with them is that: They are not hazardous to fish and invert life, they control nitrates, mulm disintegrates to the point where it sifts into the sand to provide yum yums for blackworms and rooted aquatic plants, that even plants requiring rich planting media will thrive once the sand/mulm layer is established, they do not require stirring or vacuuming, that cories and kuhli loaches love DSBs, and that my water is consistently of good quality. I know not everyone's experience agrees with mine and I believe that is because of the differences between our particular FWDSBs. My theory is that my DSB works the way it does is because of the planaria, cali blackworms, mts, rooted plants, and because the sand is coarse with rounded grains and doesn't pack down very much at all. I'd love to see a discussion about the different variables that can go into a FWDSB and what works how and why (or why not). Though my tank is not a Walstad tank, it is inspired and informed by her method and information as presented in "Ecology of the Planted Aquarium." I suggest that book as a great source of information about nutrients, bacteria, lighting, etc., comprehensible to the layperson Forgive me for trying to start another big information thread but the topics just seem so interesting!