I've had this problem too. I do 30 % weekly changes with gravel cleaning. I will try to reduce feeding amounts. Do you think I will need to clean rocks, decorations? Or, Will this go away with reduced feeding and keeping up the water changes?
i noticed a smell once when i opened th lid. i wiped down the glass and the trim that holds it ,both sides and the smell went away. there was alot of slimey stuff under there that i think will cause a smell.