broken heater

So I got home today and the heater in my tank was broken in half. I immediately took it out of the tank and went and bought a new one. I was just wondering if there's any issues that may have caused. All the fish are acting fine but there was what it looked like a chemical buildup, brown foam...

so my heater has busted, and now there's this silicon carbide sand in my tank, is it safe to leave there or do I need to get it the heck out?