I believe it's Macrognathus circumcinctus not positive though
starry night eel. Mine is prolly close too 12" atm.. I keep it in the same tank with my juvi fire eel and they get along very well, there are also small fish in the tank that have been left alone... my fire eel is more aggressive. They are like spaghetti string no matter how much you feed them they just grow longer not fatter... they do look similar to zig zags but there are some deffinate differences.
I wouldn't be surprized if they get bigger.. mines less then 1yr old and already in the "captive max" range.