Greg Sage is an expert with these and similar fish (and others as well).
Poecilia velifera article
If you read through the care he uses for the fish he keeps you will see a really good picture of care and using water keeping to gain the highest quality fish possible.
Excellent person and has very high quality fish. I have seen the fish room he keeps and it is large and well kept!
These are really amazing looking fish! In his tour he emphasized they were slow to grow.