I find that their aggressiveness is heightened during warm temps.
They come from Southern Brazil, Argentina and Uruguay which is more temperate than northern tropics of the Amazon, in fact temps can be quite cool during the winter and at night there.
So I kept them at room temp, without a heater in the same way I'd keep northern Mexican species like beanii, bartoni, or carpintus.
In fact I had a pair or regular braziliensus spawn in a 300 gallon rubbermaid tub outside in Milwaukee where water temps in the tub barely rose above 70 in summer, and at night hit the low 60s and even high 50sF.