Now we're cooking with gas!

Added a sump tank.  This is a "CHOP PIST design.  "Constant Height One Pump, Pump In Sump Tank"

This allows the fish (green tub) to keep water at a constant level.  The grow bed fills up to 7" then empties out into the sump tank.   Meanwhile the fish tank remains full and gets constant fresh water from the sump.  

20 minute fill time, 3.5 minute drain out.   That will decrease when media is added.  Hopefully not too much.  Goal is 15 minute cycles.  

GB  is 24"x24"x9"   = 17 gallons ( filled to 7" ) 

FT = 26 gallons

Sump = 26 gallons

I'm liking this setup!