Hey Ruth.....

Welcome to the board.... :mrgreen:

If you have a float switch in your sump or in your tank this can be wired to a relay box with a 3 prong plug you can use for a pump or a sevo valve that will open and close a ro line (if you have a preasure tank on it)

talk to NEWGUY he made and shipped a great set up to me at a very good price.

good luck

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

PM'd Newguy

Have a Look here.
 

Hi Ruth
Have a look at this.

http://www.californiareefs.com/forsale.htm

He does have setups for both sumps and tanks mounts. At least it will give you an idea on what you want or need.
Dave.