My corys (black sail, some say, though no one's really sure) spend most of their time hiding out, so I rarely get a look at more than one or two at a time, and then only if I try to find them.
Today, though, one came out into the open, and it looked odd. Smaller than the others, and darker:
He was hanging out separately from the others and seemed more sedate, though that's difficult to say for sure (as a group they often have long periods where they sit quietly).
Here are the others (seven in total, but hard to get a pic of them all):
How on earth could its coloring change so drastically? Further, it's smaller than the others (though they might have grown in the months I've had them).
The corys get the remains of what the cardinal tetras don't get (Fluval tropical flake, periodic live black worms) as well as sinking pellets or wafers (Hikari Sinking wafers and Omega One Shrimp Pellets--alternating days, not both at once) to supplement because the other guys are pretty good at intercepting the other food.
Ammonia & nitrites are 0; nitrates are 10. pH is about 7.5, temp is 77.