The Juwel 120 is a great Aquarium but its pump is on the rather energetic end of things. I experimented with a lot of diffusers and finally ended up using a random one that had just one downside: It was straight. The pump outlet of the Juwel 120 is angled at 45 degrees, so the diffuser poked through the water surface. This fixes that by using a simple elbow before the actual diffuser part.

Inspired by https://www.printables.com/model/543957-aquarium-pump-outlet-nozzlediffuser-for-165cm-outp