Here's some of that Porrett Foam Deeda was mentioning, just as it arrived and uncut.
I wanted enough, to stand vertically as a wall in my sump.
Here its cut to fit, it separates my pump, and biomedia section, from the planted section
I use shrimp in the planted section to help break down chunky detritus, and police gunk from the surface of, and in the porous parts of the foam.
When the foam gets plugged, I pull it and spray it out in the garden, with the garden hose.
My sump is a 6ft, 125 gal tank, run almost full.
As you can see, the pump bio-media section is about 15% of the sumps volume, and the only semblance of a baffle, is the Porrett wall.
The other 85% is heavily planted, with aquatic and terrestrial plants
The Porret Foam has been in use for about 4 years, and still viable (installed in Dec 2020).
My water parameters below
Left ammonia, next to it nitrite, and right nitrate
Another test below