Here is a picture of the hang on the back(HOB) type. The Rio 1000 is driving the reactor.

The black drip valve and connecting lines are the venturi loop, about 2" down from the top of the reactor.
The next closest clear tubing out of the reactor is the air/CO2 purge, this just extends into the top of the reactor, maybe 1/4".
The clear tubing farthest away is the CO2 injection which extends 12" into the reactor.

The black 1/2" U tube is the sump return and the 3/4" threaded 90's beyond that are the reactor return.

Hope this helps.