My Venturi Aerator and Pump Timer

The design I chose for the water return underneath the growbed that feeds directly into the fish tank provides a fair amount of aeration, but I have been worried about it not being enough when I add fish to the tank.  Many of the aquaponics blogs say that more O2 helps with the cycle too.

Okay, so how do I aerate? Aquarium bubbler(s) or venturi setup?  My water line into the growbed is actually throttled way back, so I could easily add a T to the line from the pump and throw water back into the fish tank with some extra oxygen.

I found a YouTube video called, "simple "T" venturi...cheap and effective".  My plumbing was a 3/4 T, a 3/4 ball valve, a 3/4 90 deg turn and then a 3/4 to 1" T, a 1" inner cap, a 2' long 1" pipe and a bic pen.

The picture on the left shows the hole in the end cap and the pen with a strip of duct tape to help with a simple seal.

The venturi is simple.  The T will face up and down.  Put the 1" cap in the top of the T and insert the pen to the point where the pen is past the opening for the 3/4 side tube.  This way the water will flow from a 3/4 to a larger diameter, 1" tube and pull a vacuum on the pen.  Air will be mixed as the water flows down into the tank.

Timer on the Water Pump
I also added an outdoor 24 timer that has 15 minute increments on the water pump.  I set it to turn on 15 minutes every hour.  Since my water is fed from the top of the growbed I had to add a small hole to the stand tube so that when the water cuts off, the bed isn't half full of water.  A small hole should be enough to drain it between pump cycles.

Update - March 1, 2013 I pulled the water pump off of the timer.  The cycle isn't perfect and fish will require the constant air. The drop light is on it now set to turn on at night and off during the day.  The south Louisiana nights are below 45, but our days are 65+.

Update - April 1, 2013 I put the growbed water pump back on the timer.  I have 2 pumps now, a 300 gph pump wide open and feeding the fish tank and a 650 gph throttled way back feeding the growbed for 15 minutes an hour.  FYI, my system is now CHIFT PIST.