Girlfish Power!

One of the guppies is pregnant. Really, really pregnant. I thought she had some sort of rot thing, as she had this spot on her belly. Then I thought maybe it was just her coloration. Then, the spot began to blacken and her belly to bloat. This is apparently a "gravid spot".

(The female guppy) "can also store sperm for many months to use it later (called superfoetation). It is common for newly bought female guppies to give birth months after being obtained even when kept in a tank devoid of males."
source

Female guppies deliver their young live, rather than laying eggs. Unfortunately, they have a nasty habit of eating their

fry
noun, singular and plural
1. Small fish, especially young, recently hatched fish.
2. The young of certain other animals.
3. Individuals, especially young or insignificant persons.
"fry." The American Heritage® Dictionary of the English Language, Fourth Edition. Houghton Mifflin Company, 2004. Answers.com 10 Mar. 2006. http://www.answers.com/topic/fry