http://badmanstropicalfish.com/articles/article5.html
http://boeing_dude.tripod.com/id62.htm - says no salt for scaleless
Here is a good explanation I got from the usenet:
Clown Loaches are considered a "scaleless" fish which means they
have more of a skin rather than a layer of scales. hard scales protect a fish,
not only from physical hard, but also as a way of keeping chemical products
from disfusing into their body. Clown Loaches do not have this, so they are
particularly sensative to additived to the water that might be irritating
such as medications or salts as it can be absorbed into their bodies much
easier and faster than fish with a protective scaled body.
It is kind of like how we have skin and our skin protects us from stuff. So
you go swimming in the ocean and it normally does not bother you. But notice
if you get a lot of salt water in sensative membrane areas such as your eyes
or in your mouth. They can be irritated or the way your mouth kind of puckers
up when you get to much slat water in it. Now imagine how irritating it
would be to swim in the ocean if your skin was replaced by these less
resistant tissues. That is the problem clown loaches and other "scaleless"
fish have.