Corydoras Catfish

I've reappeared!
This is a peppered Corydoras Catfish. It's real cute, and I've had a hard time getting a good shot of it. I worry about it, though. I can see the gills rather distinctly, and I know the water's good, I've tested it. There are three guppies in the tank, and they're all doing fine. I thought I'd get my cory a companion sometime soon, but I read somewhere that they get territorial and fight to the death?! It's only a ten gallon tank, and there's only one shelter.