when I came home tonight, my pregnant platy was hiding under the breeding grass. She is huge and looks like she is going to pop. You can see a bunch of baby fry eyes and she looks reddish right at the end of her stomach. Her stomach is also flat. I had put her in the breeder at 6:45 pm and it's now 9:32 pm and the only thing she's making is a pile of poop. I don't want to move her out and then back again. How long can I keep her in there?

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Never under estimate the power of an empty fish tank

In my opinion you should not keep the platy herself in the breeder. The plastic kind of breeders are used to keep only the fry. What I do is I let me live bearer give birth then catch all the little ones and put them into the breeders. I kept my fry in the breeders for about a month, because at about 3 months the fry get to about 3/4 inch big. So if I would be you I would try to figure out what you are going to do with them. In my case I started up a 10 gallon aquarium and let them grow in there for now until my lfs takes them off my hands.