I don't see why you couldn't put used salt water through a distiller
and reclaim almost all of it.

Why would you want to do this? What are the benefits?

Well, you see when you distill water you separate the pure water from
all other dissolved minerals. You can take salt water and distill it
and what you get is pure water and a pile of salt and other minerals.
You do this by boiling the water off and then condensing it somewhere
else. When you boil the water the vapor that is formed only contains
H2O, everything else is left behind.

It is possible that aquarium water contains low boiling trace organics that
would also distill over, I'm not sure.

He would be better off collecting rain water and distilling it.

SNIP

Again, the goal here is to conserve water. I am not sure there was
also any incentive to reuse the salt.

How would you reuse the salt?
It would be next to impossible to separate the water soluble organic crap
from the salt.


Lastly, why are you doing water changes to begin with? I don't do water
changes and my fish, inverts and live rock are doing fine.

That's very good for you, congratulations. However, I believe the this
subject is probably beyond the scope of this discussion.

Au contraire! This subject is the very answer to his problem. No water
changes = ultimate water conservation.