Molly Fry size

[scruffy]

I am really fascinated by the differences in birth size with some of my mollies. Sometimes I see little miniature mollies that look and get around just like the grown-ups and are no bigger than an explanation point in a book. Then I see my mollies giving birth to birth to babies twice as big. What gives?

I thought it was the age of the mother, but I just had a molly no more than a few months old give birth to the big honking kind. I've also had more mature mollies give birth to the little kind. I feed them all the same diet, and I am don't think parameters are a feature because I've had both kinds in different tanks. My mollies are all a mix of sailfin, lyretail, generic (black) molly, and maybe a little balloon molly thrown in. Do you think it's genetics?

Thanks,
Scruffy

[troy]

It depends on what size the brood is, water quality, whether the tank is cowded or not, etc. Sometimes they just have small or large fry I guess.