Re: Blackest Night Batman and Blackest Night #3 spoilers
But zombie-Firestorm says the line that good-Firestorm's rage is like a never-ending battery, as the "Black Lantern power level" keeps rising. Not due to Gen's heart being consumed, by the anger of the dude watching her die.
And Indigo-1 says something similar, as does Mera. It's emotional intensity that these things are feeding off. When Mera was able to calm down, they couldn't follow her. Which makes sense given that the Black Rings couldn't ressurrect Dove, because he was "at peace".