Slight Browning On My Heater

[Tw3lv3]

I have just noticed slight browning on my heater around where the plastic holder grips the heater would it be fine to clean it off in siphoned off water during my next maintenance or would it damage the heater?

Thanks,
Tw3lv3.

 

[aaronnorth]

it is diatoms, just scrub it off.

 

[Tw3lv3]

cool thanks mate