I've kept a few in a small 15L tank for a while but as Sam said by the time you get some moss/plants there isn't much room left.
30L odd would be a good size. I would add a bit of driftwood, riversand substrate and some plants like Hydrocotyle spp, Hygrophila polysperma, Ludwigia repens etc (most of the plants that you will find in the Waikato are pest plants). They do like a bit of flow but not too much so an air stone should do fine. As for temp - they will die at about 26 deg and will only have a short life at temps above 23-25, but saying that some people clam that the do fine at 25-26 deg. The eat detritus and bio-films (algae and bacteria) so little extra feeding is needed in an established tank but a few grains of fish food wouldn't go amiss.
As the male ages it under goes a sex change to female - so any that are over about 15mm? * will be female. Females that are in berry (carrying eggs) don't tend to do well in the aquarium and die quite fast after losing their eggs. The young larvae have to go to sea so I don't believe that they have been breed in the home aquarium.
* Cant remember the size off the top of my head but think it was around that size.