bout 99% of the time
No...but they usually do.
No, they quite often do when they are resting under a log, or searching for food under leaves etc. But they swim normally to look for food on the bottom.
With most fish, being upside down is a bad sign, but it's normal for upside down cats.
have a look on his/her body if it has 3 vertical bands down the sides of its body it indicates stress also upside down catfish dont like a lot of light they feed from the floating foods hope this helps u out
Upside-down catfishes, you mean?
No, they swim in any position-- upside down, rightside up, perpendicular-- the strange thing is they don't seem to care.
The name "upside-down cat" has been applied not just to Synodontis nigriventris, which is THE classic upside-down catfish, but to all the species in the genus Synodontis (which is native to Africa and includes at least 100 species). S. nigriventris does seem to prefer swimming upside down, although it can swim the other way just as well, and some of the other Synodontis catfishes also swim upside down frequently, but not all of them do. There is also an "Asian upside down catfish," Mystus leucophasis, which is not closely related to the Synodontis catfishes but does swim upside down.
Synodontis nigriventris seems to be peculiarly adapted to swim upside down. Its belly is darker-colored than its back, which is the opposite of the vast majority of fishes (most fishes have darker backs and lighter bellies). The species name "nigriventris" (Latin for "black belly") refers to this characteristic, which is known scientifically as "negative countershading."