Originally Posted by Brookster123
Look for a 3/4" male to male nylon barb and hose clamps..
Given the commonly parts you will probably need a 3/4 inch female hose adapter to <something else> and than <something else> to 5/8 or 1/2 hose barb depending on your particular siphon. But that would make a connection that seems fairly useless on the surface.
I think we could provide better advice if we understood the application. If you are trying to build a DIY water changer you will also need either a pump or a venturi.