The Pelican is just a really big multistage filter with capacity for an entire house...it adds nothing to the water, just takes all impurities out.
I use one with a salt free water softener.
It's supposed to be one of the better water filters for home use.
Check it out:
www.pelicanwater.com
My water is so soft that I need to keep bags of crushed coral in my sump.
My two are doing great and are more aggressive than the others.
Something like this system may be worth looking into, especially since exotic fish are so expensive these days.