I went to the pool store and obtained this gooy, messy blue stuff the first time, when I went back I got a clear type in a tube and it is great no mess.
for the intake you can use 1" and exhaust 1/2" it is much easier then working a duel in..... the Nu-clear when purchased new comes with 1", 3/4" and 1/2" for the intake side.... you can email Paul and he will get back to you very quick, see if you can purchase them from him or at the local hardware store.
more food for thought, you are planning on setting up the first canister as a bio, where will you have mechanical filtration? that means you will be pulling the waist out of the water with the bio media???
I am not sure that will give you the out come you are looking for....