Really? Oo; I always referred to what was in my filter cartridges as activated carbon xD Then again, never had an Emperor.........forgive my limited knowledge in the technical area of fish keeping ^^;
Never had or looked into Midas myself, though my LPS has one they keep in....oh its probably at least a 60 gallon tank. He's full grown, must be over a foot. Seems very happy with the attention he gets from the customers
But I remember reading on his little info thing that he is very aggressive and therefore kept on his own.
I probably wouldn't keep the Oscars and him together....or even the Oscars together unless the tank was well over 100 gallons and even then you may have issues as they mature.....good to know your upgrading though
He probably is just playing around, its definitely not something you should be concerned about.
.....Unless you have any live plants xD