So I have a 40 breeder set up for my 7 year old. Pink gravel, resin castle and pirate skull, and lots of plants, with a nonsensical melange of community fish from South and Central America, Asia, and Indonesia. I got her 6 Panda Cories, and I was concerned, because one of them never seemed to grow. All the others were growing, but one was always about the same size as when I bought them. Then last week the darn thing Shrank.
The fish that was smaller than the rest of the shoal was all of a sudden much smaller. Puzzling.
So I counted the fish. 1,2,3,4,5,6...7....8. Aha! And just to confirm my suspicions, when I cleaned the filter, I found number 9 - all of 3/16" long. Sneaky little mothers have been spawning on me.
Haven't been able to get a good picture of the fish, but here's a link to the tank: What are little girl fish made of?