Appropriate temp range in my aquarium?

I have a 29 gallon tank with cardinals, a cory and a few black skirt tetras. ive always been slightly confused about temperature. i use a standard dial heater with an inkbird controller. i usually had it set to 77f to where it would turn on if the temp reached 76 and go up. but being in california its gotten pretty hot so it gets a bit higher like 78-80. so i looked up temperature and im a bit confused. is the tempurature for my fish actually able to have a wider range than i thought? according to the numbers i see maybe. what do you think i should be doing? should i set the temp higher?

 

In the Amazon and Orinoco basins where your fish originate the temp range is from 22°C to 35°C depending on weather and season. The average is at 27°C.
Farmbred fish are bred and kept at slightly lower 24-25°C in order to keep bacterial infections under control that otherwise would destroy high density stocks.
The reason we as hobbyists keep the temp in a certain range is that stability of all parameters keeps the environmental strains on the fishes immune systems at a minimum and prolongs the life span of exotherm animals.
If we let the temp and other parameters fluctuate like in nature the fish are likely to get sick more often and die earlier.
Downside is that most fish nowerdays only can stand temp fluctuations of +/- 3-4°C (with changes taking place over a short time like 1-4 hours) and pH fluctuations of about 1 pH-point (within 1-3 hours).
In nature these changes might occur within shorter timeframes (temp even within minutes) and can be as high as +/-10°C and 3-4 pH-points. You confront farmbred fish with that and you have a tank full of dead fish within hours or days.

I might add: Your cardinals are most likely wild caught. There has been a study finding that at 18°C min and 36°C max the survival rate is 0%, meaning those are the extreme levels they can withstand. Just for their healths' sake keep it some degrees away from these readings.

 

In the Amazon and Orinoco basins where your fish originate the temp range is from 22°C to 35°C depending on weather and season. The average is at 27°C.
Farmbred fish are bred and kept at slightly lower 24-25°C in order to keep bacterial infections under control that otherwise would destroy high density stocks.
The reason we as hobbyists keep the temp in a certain range is that stability of all parameters keeps the environmental strains on the fishes immune systems at a minimum and prolongs the life span of exotherm animals.
If we let the temp and other parameters fluctuate like in nature the fish are likely to get sick more often and die earlier.
Downside is that most fish nowerdays only can stand temp fluctuations of +/- 3-4°C (with changes taking place over a short time like 1-4 hours) and pH fluctuations of about 1 pH-point (within 1-3 hours).
In nature these changes might occur within shorter timeframes (temp even within minutes) and can be as high as +/-10°C and 3-4 pH-points. You confront farmbred fish with that and you have a tank full of dead fish within hours or days.

I might add: Your cardinals are most likely wild caught. There has been a study finding that at 18°C min and 36°C max the survival rate is 0%, meaning those are the extreme levels they can withstand. Just for their healths' sake keep it some degrees away from these readings.

seems 25c is the sweet spot. which i had it at for a while. so i should not worry about my tank reaching like even as high as 29c? is that a safe range? i currently have my inkbird target set to like 25.5c with a - range of 1c meaning that once it hits 24c it will start heating back up to 25. i have the + range of 3c but i dont really have any thing plugged into cool it like a chiller anything. it just turns a green light on to try cooling even though nothing is in there ><

 

As at 30°C the Oxygen levels drop dangerously low, 29°C is when I would open the cover and put a fan next to it. That alone can cool down by up to 4°C, but also evaporates up to several liters a day.
You don't need a chiller unless the room temp can go as high as 35°C or the fish have to be cooled down by more than 7-8°.

 

As at 30°C the Oxygen levels drop dangerously low, 29°C is when I would open the cover and put a fan next to it. That alone can cool down by up to 4°C, but also evaporates up to several liters a day.
You don't need a chiller unless the room temp can go as high as 35°C or the fish have to be cooled down by more than 7-8°.

its currently at 26.1° with a 25° target i guess according to your information i should not worry so much =)

 

Not at all a reason to worry. I'm in a heatwave here aswell and live right under the roof, had 33°C air temp in my flat last thursday, water temp was at ~27°C max. I just topped off the evaporation with cold RO, keeping it at 27.
At 27° get things prepared to cool the tank down somehow, at 28° put measures into action, that's all you have to do.