question regarding dicus

Question
i am from India.Its winter now.22 degree centigrade being the room temperature at night.i bought a medium sized strained discus (Red tiger discus).I bought it at night,( i have a thermostat and well oxygenated clear water,big spaced aquarium).it was active at night;even in the morning when i gave food,it was fine and active.suddenly it started to flip up and down;ending in resting on the bottom of the aquarium;literally gasping for breathe.after sometime it died,although i found
1)it was physically fit as found by me by visual examination
2)it was not given too much food even
3)water was clean
4)water was oxygenated
5)the temperature was maintained by a thermostat
cud u please point out the reason as to why it died?discus are costly.a single piece is like 1200 bucks.so it hurts.money doesn't matter that much..just a number,whats important for me is the life.please advice.

Answer
Hi Rameez,

There can be many things that have caused your discus to die. For example, even if the water is clean, the pH levels could have been unsuitable for discus fish. Other possibilities could have been stress due to quick change in the water's temperature as the temperature from the discus' previous container is often different from your aquarium's water temperature. Another possibility is that the discus you purchased was probably already carried a disease that could not be examined with the naked eye.

Hope this helps!

-Sam