Hi Here's my predicament: I recently adopted the hobby and purchased a 75 gallon fish tank. I have it set up with a 300W eheim heater and a fluval 406 canister. It also has 2 bubblers, a limestone fixture and a large piece of drift wood atop around 2 inches of pebble substrate. Around a week ago i had recieved my first heater and was preparing to start the nitrogen cycle (with 10% ammonia) however the heater arrived broken. I let the water sit in the tank with the pump active until yesterday when my replacement heater arrived. I've now started the ammonia cycle by adding 4 PPM. My problem is this: whenever i lift the hood of my aquarium the skim of the water smells musty. I think it might be the drift wood but i am not sure. I have a bubbler placed behind the drift wood. Also the tank water is about 86F degrees if that helps any. Thankyou!