Mold and Fish Tanks

I'm wondering if anyone has had a problem with mold and fish tanks. I recently (Sept 4th) moved into a new home I am renting. I am having to scrub mold off the walls in certain places with bleach that keeps reappearing. I am pretty certain it is not my 40 breeder tank as I only replace about 3/4 gallon per day in evap and haven't had this issue before with a bigger tank. I want to tell the owner of the property, but want to prepare myself first as I think he will just try to pin it on me and it being the tanks fault. I am pretty certain this was here before and was just cleaned and covered up during the showing. There is no mold on or around my tank, stand, canopy. Has anyone experienced this before and dealing with a property owner? I may need to break my lease, but figured I would start here for advice and then talk to a lawyer before going to the owner.