Whole house water filtration systems

Seems like a waste of money to me. Municipalities have to meet EPA standards, our fish do fine with dechlorinated tap water.

I can't imagine it's doing anything beneficial that something cheaper could do a la a dechlorinating product...and if you're really worried about TDS, a good RO/DI unit would cost a lot less, but maybe not as quick for filling purposes.

Also interesting that they even state that it's only been third party tested for chlorine odor/taste. So really who knows what it's doing in terms of heavy metals, TDS, VOCs, microbes, etc.

Concur with everyone else if on municipality water its likely a waste. I have regular $180 5 stage rodi system.

I did start using rodi on my freshwater tanks, now instead of using Prime I have to add Equilibrium, can't say that my fish seem to notice any difference, how ever my shrimp do seem like they may breed a bit more.

It's possible, just they aren't very specific in how well it removes anything other than specifically chlorine. You might want to dig deeper and see if there's any testing regarding TDS/GH/KH/pH or other important trace minerals (Ca, Mg, Fe, etc.)

It sounds like a water softener. If that's what it is, it probably adds salinity to the water. When I was younger, we long term house sat (2 years) for a family friend that had to go to South Korea for work. The house had a water softener. All the indoor houseplants died off, and if you knew just how green my mom's thumb is, you'd know how weird that is. When she replaced them, she started bringing water in from the outside, and the plants did that normal lush growth she coaxes out of them. I hated showering in it, because I never felt I rinsed clean. That could also be problematic for your tanks.

Good point, if there is any ion exchange going on it may be adding things you don't want...and a lot of softeners actually raise TDS given how they do the exchange.

However it is softening the water (via potassium or NaCl) it is likely not as good for aquarium use as tap water. Reverse osmosis water is the only filtration system that I can safely say is best for aquarium use, but only if you reconstitute it (and do so with a certain amount of consistency and precision).

Contrary to popular belief, hard water can be a blessing in aquaria:
http://www.wetwebmedia.com/fwsubwebindex/fwhardness.htm