I recently added a small piece of driftwood to my water, and i also have a case of brown algae growing in the tank. My water smells now, but i cant tell what it smells like, its not a egg rotting smell, or dead fish smell, i have checked and all my fish and snails are alive and well. Should i be concerned about this, i have done about 7 water changes and i keep up with my weekly maintenence but the smell has not gone away. I have two filters running with the activated carbon in them. Any ideas?