I have to totally agree with the previous two posts. I have had an upside down cat for 8 months. It always hides, although it's spot for the past 2 months has been right behind the filter where I can at least see it. For the previous 4 months before that, I seriously thought it had died and been devoured by my big killie and angels as I had ripped the tank apart (plants and all) on several occasions looking for it and never saw a trace. Low and behold, 2 months after I had given up on it, the sneaky little bugger showed himself. I have only ever seen it swim freely around the tank twice (other than it's first day), and both those times were at night after lights-out. My tank is heavily planted, so I'm guessing that's where it gets it's food at night. It will eat frozen foods if I drop them right on him/her, but only what comes close enough to it's mouth. But oddly enough, it's a chubby little fish still. I only learned that it preferred groups of 3 or more a month or so ago. I will eventually add a couple friends for mine to try to coax it out.
Colin