Is My Tank Too Warm For Vietnamese Cardinal Minnows?

[Jeremy180]

While my tank does have a heater, it will be on the cooler side, with the heater coming on at about 75-76 degrees F (about 24c)
However, in the summer the house will be getting to about 78 degrees f (about 26c)
26 degrees celsius is the highest I've seen recommended to keep cardinal minnows at, but I'm concerned that they may be more prone to disease at those temps, or have shortened lifespans?

 

[OldMan47]

At 26ºC many fish are too warm. I keep goodeids that are known for not needing a tank heater in a typical home but some species of them do not do well without me using heavy air conditioning in the summer to keep the house cool. Needless to say I no longer try to keep those species.