Strange white crud building up on one of my heaters (50w) in my twenty gal. Also creating a film on top of the water. I took the heater out, fearing it had failed, did a 50% WC, and bingo, film gone. Anyone ever seen this before? I dont have hard water, so I doubt its mineral deposits. Especially since it created a film on top. Also had two fish die in the tank over the weekend prior to the WC. Not sure if its related. Nitrates were a little high (40), but thats not unusual for me. Tank has been runningwhite, film, for about 3 years I would guess, had 5 odessa barbs, now 3.
It was a back up heater in the tank, so no urgent need to figure this out. Just weird is all.

It was a back up heater in the tank, so no urgent need to figure this out. Just weird is all.