Tsk, tsk, piece of Eheim tubing. Make sure and keep in mind to have them at different heights in the COD! Both on the same height next to eachother won't do it, noise, you know. Have one hanging deeper and the other one above it.
Totally unrelated and certainly not helpful, but any time someone puts "Q:" in the thread title, I feel like they're asking me specifically. It makes me feel wanted, and I like that
Many thanks for all your help! What about the outlet? The one on the Eheim is smooth yet on the nozzle of the stock outlet or water diverter is threaded! What would you do there?