Thank you, haven't thought of my anode rod in years.You might actually have been generating hydrogen from the anode. When was the last time that you pulled your anode to check if it was clean and still had material on it?
Personally, I only use powered anodes as pulling anodes is just an awkward job for a part that needs to be checked, if not replaced annually. Your water heater will last a lot longer if the anode is in good shape as it mostly or completely stops the corrosion of the tank.
All the best,
Peter