Hallo!
I think I ‘ve found a solution :
I’ve talked with my local animal trader, he has all his tanks with HMF.
He has them run with one big and very silent air pump in the back room of the shop.
Now I took a very long air pipe and placed the air pump far away in the room.
Now I think it’s a good portion better, I mean I hear now only the bubbling water….
You see I am going to be a bit of obsessive in this affair ….. 😉
And that’s an explanation for the fact that obviously the aquaristic Profis don’t matter about that fact: when they have one big air pump for all tanks, the vibrations have disappeared when the air arrives in the tank… What do you think?