my 131g FOWLR

[golf nut]

Originally Posted by kien

no that's pretty much what's happening I think?

1) Display tank drains into the water change tank and water change tank drains into the sump. Everything flows as one system.
2) Take the water change tank off line (out of the loop) by turning bypass valves so that now the display tank drains directly into the sump.
3) Water change tank is now isolated.
4) Drain the water change tank, refill and mix with new salt water.
5) Now put the water change tank back into the system by turning the bypass valves back thus forcing the new salt water through the system.

Maybe the scale is confusing if all you are doing is a 10 to 15% water change, doing what you are saying will work fine, it just seems like a lot of plumbing and space to do a water change.