Now now, don't go badmouthing haydite too much. I use it fairly frequently. I have 50 yards of it outside the greenhouse, so if you want to try it... It makes a pretty good semi-hydroponic medium. For SH, I use it straight, or mix it with diatomite. Sure is cheaper than diatomite.
I do wish it came graded, however. It is a mix of pea sized pieces and fines all the way down to dust. I use a diamond bottom plant flat to screen the larger pieces from the fines. Yes, it is a bit of hassle, but not too bad. I've contemplated a few automated systems for grading the material, just haven't gotten around to assembling the parts together. I don't usually wash it, unless you count the pile sitting outside in the snow and rain for a couple years.
The larger pieces I use in SH. The fines I usually add to peat mixes for weight and aeration. 50% peat and 50% haydite fines (or even just unscreened haydite) is an excellent bromeliad potting mix, btw. I make my own version of Aussie Gold with a bit of diatomite, haydite fines, and peat, as well. I use haydite freely as a substitute for sponge-rock. It is a bit heavier, but that is ok, otherwise it seems to behave about the same. Again, when using it as spongerock, I usually don't bother screening it all out. I like a bit of fines in my small mixes anyway (and I used to add a bit of sand to some of them, now I don't have to).