Ron. Any pics of the little fish? I may be able to help you ID it. I have about 60-70 different little fish from the keys and Atlantic coast scattered throughout my tanks lol. Already done the research through tons of species books to ID all of them, so may save you some time lol.I know from experience that RFAs as small as 1" to 1 1/2" can spawn.
Unfortunately I've never witnessed a birthing event, so I have no idea how small a RFA might be and still be able to produce offspring.
RFAs do take time to grow. I've found they grow very slowly if you rely on just photosynthesis. They do better if you are feeding the tank for fish. And even better if you are over feeding. And they do grow faster if you feed them directly every 2 to 4 weeks.
Since all but a couple of mine are now in the RFA breeding tank, they rely more on my feeding them individually. But over the last few months I have been adding some livestock in with them. First were some sexy shrimp and porcelain crabs. Then, later I started adding astraea snails, then nerites and recently stomatella snails and a very tiny, unknown fish I collected when collecting the stomatella snails. So now I do feed the RFA tank some, but I still feed either small shrimp or cut up silversides individually every 2 to 4 weeks.