here is a simple venturi

take a 3/4" ball valve
unscrew bolt holding spigot
drill hole or screw into the center of the spigot hinge holding ball in place
connect 3/16" air hose to top of spiqot

congratulations
now attach an air valve to control your bubble size- recommended pump at least 400gph for good flow. put the venturi after your water pump on a verticle plane or downwards angle and make sure it draws a vacuum in the airline. the water being pumped to all your beds will now be a superoxygenated foam. this device is like using 10 air pumps.

you can use the venturi airline to draw in nutrients and mix them in the throat of the venturi. run a slight angle after the venturi so the mix is augmented through a vortex motion as demonstrated by bubbles when the venturi is drawing in air. the venturi is used to mix fluid and gas in industrial and commercial applications.

the venturi works by drawing in air from the narrow point in a waterline
this works because the water speeds up as the waterline narrows, and
when the water passes through the valve it has to speed up through the small hole. when water speeds up, it loses its pressure and creates a negative pressure (vacuum) inside the narrow area. the vacuum draws in air and mixes it with the water very efficiently. depending on adjustments made to the shape of the airhole, power of pump, gravity, length of line, and angulature of line there is a greater degree of efficiency (finer bubbles, more air mixed with less water resistance). This fitting is very easy to make and is worth the time.