Just some interesting products to note from a company called Genesis Reef Systems. Genesis is based out of Ohio and specializes in water change/water top-off systems.
The Genesis Renew will conduct automatic water changes, but you can control how much water to change, plus you can control how long it takes to change that water. What a great idea.
So far, we don't have any experience with any of their products, but with decent price points (we are looking at around $500 USD) I imagine these will be popular for some larger reef tanks.
Not quite sure I would hook one up for a 10 gallon Goldfish tank though...as they mention!
Check out their website here.
There is also an article on Reef Builders, where I originally came across it. You can check that out here.