Ok so here goes... pretty simple... water comes down and enters sump (via overflow in tank)... gets heated, skimmed, tested, and what ever else you want... from there it is pumped back up to the tank... As it it pumped past the line comming from the fuge it draws a vacuum on that tube and pulls water from the fuge and takes it to the tank... This drops the level in the fuge and the syphen into the sump fills the fuge again...
y woudl you want to do this? notice... 1 pump... with out having to have your fuge stacked on ur sump... also the fuge water never passes through a pump... so none of your critters get chewed up...
Mainly... 1 pump... and its cool...
-me