Impeller 1
Impeller 2
Impeller 3
Double propeller aseembly. Note the flexible airline tubing just slips onto the rigid tubing (section in red) and glued inplace with CA glue. The propellers are drilled out a bit so that the (1/8" OD?) rigid airline tubing will fit through.
Assembling the prop and impeller
Completed prop/impeller mod.
Note: see how the 2 propellers are placed in such a way that they form a screw like curve. This will generate A LOT more flow than using just one propeller.