Think of it as extruded glass, and the weird shaped parts make more sense. I see some similar things in mine if I look closely, though infrequently. My GUESS is their manufacturing process may be a bit inconsistent, after all it's aimed at sand blasting not esthetics. I had no issue with oil, in fact I suspect what people see is extremely fine dust that floats. Had a fair amount of that, I just washed for a few hours. I find a continuously running hose best -- just poke it around in the sand, let it overflow and the floating stuff goes away faster.
I've had my first black sand tank going now for 9 months, I don't regret it at all. It is FAR easier to plant and replant in than gravel, and the plants seem to love it.
I've had my first black sand tank going now for 9 months, I don't regret it at all. It is FAR easier to plant and replant in than gravel, and the plants seem to love it.
