All depends on the type of fish. Doing some research is the fun part of the hobby.
x2.
If we're talking angelfish, 1m/4f would be a poor choice because they pair off prior to spawning. If you're talking mbuna, it's a common suggestion. If you had endless demand and a suitable tank, 1m/12f would work for mbuna as well.
If you have specific species in mind, toss out the name and I'm sure people will chime in with their suggestions.