I just started fishless cycling my new 5 gallon tank a few days ago. When I left for the weekend, the ammonia reading was about 2.5-3.0. When I came back, it was about the same, but there is some kind of dark yellow substance in the filter media. It appears to be clogging up the filter somewhat. Does anyone know what this is? There is nothing in the tank right now as far as decorations go, not even gravel. The only things I've put in the water are Stress Coat water conditioner, Ace brand ammonia (which should be fine from what I read) and Seachem Stability (I know there are mixed reviews on whether it actually helps, but I thought it was worth a try).