Hi. Everyone. I bought a aqua top 24 gallon couple weeks ago. Now I tried to start cycling my tank about one weeks. I found some brown thing on sand. This is my second tank. Never see this before on my first 10 gallon tank when I started. Can someone help me out? I added dr Tim one and only and dr Tim ammonium in there when I start. Now my nitrate is 5.4 ppm Pho is 0.51 ppm

