water temp is key.. In south florida water temps in the canals don't go below 72 because they are mostly box cut canals which tap into the biscayne aquifer (spring water source).. So when temps drop into the low 40's and 30's the water still stays in low 70's.. that being said peacocks have spread into the everglades and when there is the occasional freeze there is a die-off.. also species matters. mono and ocellaris can tolerate lower temps than say orinos or tems.. Another thing to consider is even in brazil these low temps only last for afew hours max before warming again.. While cichla can survive in temps as low as 60 when your start getting below 70 metabolic rate slow drastically with fin and tissue damage occuring with prolonged contact with sub 65deg. water.