They come from fast moving stream water where the water is cooler. I've never heard/seen one over 3 inches(But that's me).
Here's a little info on them
http://aqualandpetsplus.com/Oddball, Borneo Sucker.htm
woaahh, i love their body shape. really interested in keeping one. fast moving water? lol is top filter good enough for them ? but what happens if i put them in slow moving water?