Im new to fish keeping. I have started a 10 gallon tank. I used Cycle in it for the three days then let it sit for two before adding two zebra danios. Im now almost 2 weeks in and I noticed that my tank has a musty kinda earthy odor, just wondered if this was normal? Should I change water or is this nothing to worry about? My ph and amonia levels are fine. Any advice would be great