Hello all. I have a 20 gallon long that I recently changed substrate from a dirted tank with sand cap to just sand and root tabs.....I used quikrete play sand because many other people have reported no issues with it. I have experienced a nitrate spike which may be due to a mini cycle caused by the substrate change. But recently while cleaning the glass one of my magnets fell into the sand and when I picked it up it was covered in what looked like tiny tiny metal shavings like what would be left over from a grinder. Anyone know what these bits might be? I'm assuming most metals are harmful for tanks?