Bacteria will grow on almost any/every surface in the system. So we should expect an extremely thin layer of them over virtually everything.
With the exception of breeders who overstock bare tanks with no substrate for growouts, I doubt any of us have ever had a tank that had insufficient surface area to house enough bacteria for a proper nitrogen cycle even if we removed all of our "bio media".
Sponge only filters certainly will work. And as the filter clogs in one area, wherever the water continues flowing will just get more bacteria in that area.
With the exception of breeders who overstock bare tanks with no substrate for growouts, I doubt any of us have ever had a tank that had insufficient surface area to house enough bacteria for a proper nitrogen cycle even if we removed all of our "bio media".
Sponge only filters certainly will work. And as the filter clogs in one area, wherever the water continues flowing will just get more bacteria in that area.
