As has been stated before, unscrew the plug, cut the rod off and reinstall the plug. A large socket, hacksaw and some pipe dope are all that is needed to fix this problem. 20 min tops. 1/2 cup of bleach might be a bit of overkill unless you need to flash the system but a couple spoonfulls won't hurt anything. Let it sit for a bit then run the water until you cant smell chlorine at the faucets. The chemicals in your water are reacting with the rod. I don't install a water heater in this area without first cutting out the rod.
This has been done 1000's of times.
I'm not sure how yours is made but they used to have a high magnesium content in the rod and make a great sparkler once lit. Stay way back and be sure there is nothing within 100'+ that can burn.
