Heater glass cracked

[simonts]

I have just noticed that the glass around the heater has cracked leaving the heating coils bare in the water..think it may have been like this a day or so but didnt notice...have now replaced the heater with another but im just worried..would the cracked glass casing have left anything dangerous to the fish from the rest of the equipment in the water (chemicals etc)?

 

[WILDER]

Maybe do a gravel vac and water change just to be on the safe side, and run some black carbon.