Walter, I believe a Reef Filler can be placed up to 200ft. away from ones tank. They run around $299 at Mops.
Or is you wish to use something like a Tunze Osmolator. I believe several members here use them. Great top off device. The probes will go in your sump, however the top off hose is best in your tank. That prevents any back siphon.
My friends is set up as such in his 180. The probes are in his 100g sump and the kalk/top off feed hose is in the overflow.
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Doug
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