Fuel tank venting considerations

[ErikFinn]

I have an auxiliary 140L diesel tank installed by the previous owner and I'm in a process of replacing fuel lines and making sure I should have minimum problems relating to the fuel system. This aux tank is connected to the main tank via a hose and has an electric pump in between to transfer the fuel to the main tank. In addition to this hose I want to replace the aux tank vent hose, but have not yet been able to find where it leads to once it disappears under the cockpit floor.
So to make sure I'll do this properly, and buy long enough hose etc, I wanted to ask for advice on how to install this vent hose?
I suppose it should have a swan neck to prevent (or at least minimize) any water pouring in to the tank?
Also, should it have some kind of valve or filter to prevent insects and other unwanted stuff from finding their way in to the fuel tank?
Furthermore, I suppose a proper diesel or oil hose is the way to go, material wise, not just a cheap garden hose or similar?
Is there a common method or standard on how to install a diesel tank vent hose? Any links possibly, anyone?
Also, in order to follow the KISS-method I was thinking it might be a good idea to replace the electric pump with some kind of a simple manual pump, as this pump will be very rarely used, maybe a few times a year, so a manual would make the system a lot simpler, what say you?

Thanks,
Erik