In article ,
says...

Attach a piece of fabric under the AC filter cover. The size and mesh
size will determine how much it will dampen the turbulence. The fabric
hangs down into the aquarium. I'm not going to change filters everytime
a fish is not happy. I prefer to just modify the filter which is
working. hth

Great idea! Low cost and variable effects. Thanks, I'll try it.

--
Homo sapiens is a goal, not a description