Weather loaches take temps into the 50s'F and don't need a heater, that said low 70s should work, and if you got a more Brasilian strain of balzani, it should be fine.
If you get balzani, a harum of 1 male to 3 females often works very well.
I kept 2 males with 5 females, they spawned regularly, but even then aggression was un-noticed, mostly just display.