Yesterday, did the 72G pwc 65%.
Later that evening and as I went by the tank to close the shade, it was noticeably warmer on the bowfront glass than usual. Like a warming pad.
I paused and noticed heat like a sauna coming from the glass. Usually, it is a little warm next to the big 4' glass.
Checked the water and WOW, it was toasty. Fish were heavy breathing.
Added an air bubbler.
The little bobbing thermometer was broken / cracked. Grabbed the other thermometer and it gave me an obviously incorrect reading. The stick-on glass thermometer tab was off the chart. Tried to get a reading from an also not quite working correctly handheld thermo checker. I guess it was in on the cabinet because it wasn't working right. The working one was somewhere near the BBQ, according to DH.
Didn't have enough time to look. It was really hot maybe 100ish F I thought 92F, but if we are 98.6~ it was even warmer, like a lower warm temp hot tub. Opened up the lids to vent and unplugged one heater. But then in moving it, saw the one next to it was still "ON". So got that one off.
I lost at least 2 fish a Gourami and maybe the SAE. Found the degraded bodies. They had passed earlier. Not sure how long this has been going on.
Drained down about 1/3 and started a 1-2 hour process of getting the water temp a little cooler, and allow it to return to the ~80F it normally is at. I am so sad that the little fish were suffering.
Had just last week, walked past an electronic digital controller at the lfs. Wish I would have grabbed it.
Planning to get a controller for that tank. Not sure what to do with the smaller, equally at-risk tanks. Tank is back to a normal temperature.
This heater is a Fluval 100W submersible heater. I think it is the newer one I bought. It was sitting next to the other Fluval lower Watt heater in the tank.
Creamsicle is mending again. Tail looking better.