I talked to a friend of mine who suddenly lost discus overnight, he woke up and 2 were dead. he pointed the finger at the heater which stopped working, his temp was 25 degrees.
I said to him that discus don't die at those temps, as i've kept them for 2 weeks at around 25 during a trichlorofon treatment. I also forgot to turn the heater on after a water change a couple of times, they do look weird, hardly move etc. but never lost a discus because of the temp being 25C.
Can 25C kill discus? What is the minimum temperature discus can survive under for a couple of hours?