Nothing needs to be done, Fethi.
When discus is being transported by plane, the temperature can goes down all the way to 18C (64.4F far distance travel) and discus are still o.k.
*Just to add that I don't mean that it is alright to keep discus @ 18C. Short period is O.k. ...thus 76F or 24.4C is very acceptable as it is even warmer than an aircondition room*
Just on the heater to 82.4F or 28C and everthing should be o.k.
Take care,
Andrew
