All great information. I set up a 20 gal tank in December 2020. It was clear and then turned cloudy. My HOB filter has a sponge, filter floss and filter medial rings. Would it help to add a sponge filter in the tank as an extra filtration? I am sure as mentioned in this forum that when I cleaned the tank and substrate it did not help. I will just have to wait for it to clear up.