I just know when I tried to cycle a 75 gal tank last fall with fish it went very slow. I had 4 black skirt tetras and 2 white skirt tetras, 2 anubias, an amazon sword and 2 java fern. After about 8 weeks my bacteria would stay around .50 or less and I never did have any nitrites or nitrates. I ended up using Tetra Safe Start and had it going in about 10 days.