I've had them in the past. They do feed off the bottom, but they will also swim in the mid-level more, and will rest on plants in the middle of the tank, too. One thing you should know is that a school of three isn't enough like it is with larger cories. For them to be happy, you should go for 6 or 10 of them. They also appreciate a small cave to hang out in, more than the larger cories.
By the way, they're awesome fish, some of the cutest out there.