They don't need brackish water to reproduce. And if you have a male and female, chances are they will make a lot of babies very often!
They can live easily in lighted tanks, my guess is they do like the light so you will need one, but provide lots of hiding places because they are kind of jumpy.
I think they can just eat most food that end up floating to the bottom, if you keep them with fish. You can also buy algae wafers and other foods similar to that.
They don't get pregnant but they do lay eggs. The male and female will mate and soon you will see eggs on the females tale. I believe over time they will get darker and will eventually hatch and leave their mother.