I agree with angey john, if you really want to mod it- get rid of venturi and install N/W pump. (I like gen-x pumps or Ocean runners because of the much finer bubbles)
In the past, (using one now) I have used old beckett, and venturi skimmers, removing the beckett and feeding them with N/W pumps. they worked great! You can also a Hartmans (?) loop if you need more control over the water height.
The one I am running right now has been made recirculating!
