The black spot from her rotting gourami.
Anyway, back to my trough.
I've got an acrylic trough 2.5" deep with sand rinsing in the basement. The trough was meant for wall mounting so it has two screw holes where water pours out. I'm letting hot water from the basement hose trickle across it in hopes of removing anything that would have rushed out and killed my fish had I not done this. I was mounting in to my 2 x 10gallon livebearer breeding tank set up when I had second thoughts about the cleanliness of the sand.
I rinsed it over twenty times and now that the organic debris is gone it is less like clay and more like truly nice sand. It's stiff above water but very yielding (almost intangible at first) to a finger push once submerged. The average grain size also appears to fall into the correct zone, but I shook it down and the tiniest granules are at the bottom and larger ones at the top. I think that lends to a more functional sifting habitat so I'm leaving it like that.
Tomorrow I'll put screens over the exits to confine the trumpet snails which I will also buy tomorrow. I'm not worried about the worms. They probably will hunker down and stay put just fine.
The only thing to work out is the "in" flow. I have a 1/2" hose that, without intervention, will land in the center of the trough and dig a big narsty hole. I don't see any problem with said hole except for lost anaerobic potential, but would rather diffuse the return. I might try a holey piece of plastic tubing or something. The return from the trough will be the two screw holes.
One interesting thing here is that the water depth above this sand will be less than an inch. I hope the worms and snails are okay with that. Input?
The sand is riddled with pyrite. If it were gold, it would not be on top. Is the pyrite or associated minerals a threat?