I think the tank is about 76. I really dislike keeping tanks at a steady temp- I like it to go up and down like it does for real- but this is in the house and I’ll live with it until o toner when I know I it down. The various little Uruguay fry that are in there are Just dithers. I have terapurpura like some people have snails.
Common misconception to consider the southern fish “cold water” or “cool water” species. More accurate to to think of them as seasonal fish that can take high highs and low lows.
76 is pretty middle of the road. The vat they were born in gets up to 90 pretty regularly
The Uruguay fish will get as cold as it gets this fall/ winter (water in the low 50s a lot of mornings and not hitting 60 very often) but these trifasciata will go down to 65-68 or so- I have no idea how far removed this pair is from rio Paraguay (purchased as wild but…) but they should be fine anywhere from 65 to 85- and if they aren’t they’re “fake” aquarium strain strain fish too far removed from actual representation of the species to be of interest anyway.