Top up question

[monza]

Float type valves work well and are real easy. If you want the bling bling get one of these. Tunze Osmolator Universal 3155 http://www.tunze.com/usa/index.html?lang=en-gb (click on other components)
It keeps water levels pretty much exact. A bit spendy but a slick piece of hardware.

I use a float valve in my RO/DI water top up storage (salt bucket) the Tunze pumps water from there to my reef.

Also water can flow from my small salt bucket storage to a large rubbermaid for salt water make up controlled by another float switch.

Dave