The Rača 4 is a cyprinid district, starting from the confluence with Radomlja in Dob (near Močilnik) and flowing into Kamniška Bistrica. Rača, Radomlja and Radomeljska Mlinščica are joined into the brook. From the confluence, the channel is regulated and deeper and covered with a high branch. It is rich mainly with cyprinid fish species, including the nase.