<a href=showthread.php?s=&postid=6705175#post6705175 target=_blank>Originally posted</a> by Dwayne
These will get you pointed in the right direction.
http://reefkeeping.com/issues/2002-07/ds/index.php
http://reefkeeping.com/issues/2003-07/nftt/index.php
FWIW.
<a href=showthread.php?s=&postid=6729261#post6729261 target=_blank>Originally posted</a> by joedirt
What if you made the top section Exactly like the middle section, with the surge tube. Then tap off your return pump and drip into the top section. This way it is completely self sufficient and salinity swings wouldn't be an issue.