They are fairly typical rainbows. Prefer slightly harder and alkali water, but are pretty adaptable. They do not tolerate pollution, so water quality is more important then conditions.
There are numerous species of Pseudomugil, they will all interbreed with each other, thus it you should not keep more then one species in a tank, (or keep single sex groups). Breeding is typical rainbow. The eggs take ages to hatch, (like 2 weeks or more), many a spawning has been lost because they have simply been chucked away. Small fry with the problems that creates, and like other rainbows, I found the fry "stick" after a couple of weeks and really don't grow at all - they cath up later though.