It's really not that unusual. I dont know how long u have owned this aquarium but after awhile dust builds up on the fan blades. When this happens it causes the blades to become unbalanced, causing a vibration. When it happens on my BioCube, I take the fan assembly apart and blow the blades off with canned air. The same stuff u use on electronics It's no big deal. All u really need is a tiny Phillips head screwdriver. The kind u would use for glasses and a can of compressed air. U can get both these at any Walmart or home improvement store