"mike d." wrote in message
. ..
Personally, I believe that when the salinity is highly excessive, it
builds up on the exterior much more readily and with more mass. I
usually just add pure water, and then monitor the hydrometer
readings to ensurew that i maintain adequate salt levels. Mike.
"Tom" wrote in message
om...
I always hear that when water evaporates, you just need to add
unsalted water, since the salt is still in the tank.

This is true. Use RI/DO water or distilled.

I don't do this,
I always add salt, and my salinity is pretty constant. I do have
lots
of salt up around my light and on the top edges of the tank. Why
is
this?

It's called 'salt creep'. And is giving you a false reading + it will
eventually kill your equiptment. Clean it all off with tap water. You
woun't like it when/if a chunk of it drops off into your tank.

Also clean your SG meter (the swing arm type) with vinegar to clean
it.