I have these little white things on my tank (sorry no picture) but they look like mini-mini snails.....they are also hard to scrape off. I was just wondering if anyone knew what they were.
That's not a ton of description, but I'll hazard a guess that it's a kind of foraminiferan. At least you sound kind of like I did when I found these guys in the Hitch Hiker FAQ. Take a look at:
and scroll down to the second to last entry on that page. The description starts with "I have a bunch of these little things that remind me exactly of tiny grindstones."