To add to the debate about cory activity level on the first page. The activity level of cories depends on several things like their age, the ratio of males to females in the tank, group size, and their species. For example my younger male swims a ton on the bottom and the younger female is always harassing the males to try and spawn. My 1.5 year old cory only scuttles around a little, goes up for air occasionally, but mostly just sits still and watches the younger ones play. Larger groups actually tend to decrease in my activity. If you keep just one or two cories they tend to glass surf in my experience since they are tyring to school with their reflection. Some cory species aren't particularly active while others swim a lot. Even the less active cories still do "scuttle" around as Sakura said.
If you get cories though you really do need to keep them in groups of no less than four of the same species. Some people keep different species together in groups less than the absolute minimum but that is not very advised. Cories tend to be more stressed when the don't have their groups of the same species and different species will only school together out of necessity. When you keep cories in the proper group size you can definitely see a difference in behavior.
In a ten gallon you could actually keep C. aeneus. They are a bit big for the tank but a small group of four would be okay. That's what I keep and I find that they tend to settle down as they get older and bigger. C. aeneus comes in three color variations:bronze, albino, and green. If you do get green cories make sure they are actually C. aeneus and not emerald cories. Emerald cories are not actually cories at all but in the same family and get to be a little over 4 inches long.