In the mid 1960's I was raising tropical fish. I noticed that some Guppieswere more transparent.
I decided to see if I could make a transparent breed of Guppies by selective breeding.
How do Guppies give birth and how often will they give birth?
Number of Offspring. Once a female guppy is 2 or 3 months old, she tends to start giving birth. A female guppy under optimal conditions can give birth every 30 days -- and each batch of fry can range from 20 to 50 baby guppies.
By selective breeding within two years I had a breed of see threw Guppies.