The cheap glass heater in my mantis nanocube exploded a few minutes ago - Deb was in the room and said she heard a pop, followed by smoke coming out the vents. She unplugged everything and called me - when I got there to take a look the heater was shattered and there was a bunch of dark film floating on the surface of the sump. I pulled out the heater and all the parts I could find, but I don't know what may have gotten into the water. What's inside a heater?

I'm running a healthy sockfull of carbon and can do some big water changes quickly if need be. What should I be concerned about?

Chris