https://www.ebay.com/itm/185181577315
So i was looking for some substrate for a small tank, and came across these things. They are twice as expensive as normal gravel substrate... and take forever to ship, but I think I am going to get some and do the vinegar test and stuff on them to see if they are safe for the fish. Maybe i can get some really sparkly ones for a few bucks more...
Do does anyone have any suggestions as to what to try to prove their safety in the water long term? This obviously isn't practical for larger tanks, but a small 5-10 gallon tank might be neat.