Hi Rich,
ok, I understand your worries now. If you don't feel comfortable with this type of sand, just don't use it.
I'm using fine black gravel, size 1 - 2 mm. It's plastic covered (I hope plastic is the right term here; the german word is "Kunststoff"), so it has no sharp edges.
Again, there's a rumor in the german community that this gravel is toxic. It is said that when the axies swallow it, the plastic coating is dissolved by the gastric acid and causes serious issues.
I can't confirm this. When my sweeties got ill and and had to be put to sleep, the autopsy said it was bacteriae infection. Not the slightest sign of poisoning, besides the bacteriae, they were in perfect condition.
They'd been sitting on the black gravel for almost six years, so I think it's safe.
You could use a black sponge that doubles as filter. This way there is nothing in the aquarium that could be swallowed accidentally and cause troubles.
Depends on what you're feeding - if you're feeding pellets, fish, earthworms etc, this type of filter will be fine. Snails and other small creatures may get stuck in the sponge.
Cleaning this kind of filter might be time-consuming, but I know several people who use it and are really confident and the axies seem to like it, too.
