Interesting thought. I do wonder if the water can exert enough pressure to push through the skin and onto the scales. Like when you hold a fish, you exert pressure on the skin covering the scales which is transfered to the scales. But holding a fish, or when a fish tries to get out of a tight spot backwards is much more pressure than water flowing over scales covered by skin and slime.chefkeith wrote: It's just a theory from my observations and experience.
It's when the water or anything else goes against the grain of their body. Their slime coat and scale pattern adds a layer of protection, but if the something is rubbing the wrong way against their scales it probably feels like a bug is crawling on them. Now I'm getting itchy just talking about it.
To put it another way, loaches have no problem getting into tight hidey holes head first, but they may have problems getting out of holes going backwards. That's because there is more friction going back to front than there is from front to back.
Another example, is if you ever held a fish in your hands you'd know how slippery they are when you hold them tail up, head down. But if you hold them head up, tail down they won't slip through your hands as easily because of the friction from the scales.
( I know this from handling fish when I was a chef. Obviously, I wouldn't do this with my pet fish.)
It does make me wonder about the waterflow in my tank and how fish would experience it. The waterflow in my tank is high, but also chaotic. Could be that they experience it as annoying.