We are pretty new with our aquarium, and I have been researching different ways to go with it, but I have a question. We have two platy, a fancy guppy and a cory cat in a 20g tank. The sunburst platy, which we have had a couple weeks, is female, and much to my surprise, LOL...I think she was pregnant. I went to the fish store, and got her the little plastic floating cage for her. Also, the past week, before I separated her, the guppy, which is a fancy blue male of some sort...my son would remember exactly what kind...he had started chasing the platy all over the tank. I thought that guppies and platys were ok together??
Well, after having her three days in the little floating thingy, she doesn't look pregnant any longer. I took her out and put her back in the tank. The guppy once again, started chasing her and nipping at her. What would be the reason for this? Is it a male female thing? or ?? I believe that the other platy we have is a male. I didn't do any of the sexing of the fish, as I new nothing at the time, but now I am thinking I need to make some changes, and I am not sure what to change?
Any suggestions?
Well, after having her three days in the little floating thingy, she doesn't look pregnant any longer. I took her out and put her back in the tank. The guppy once again, started chasing her and nipping at her. What would be the reason for this? Is it a male female thing? or ?? I believe that the other platy we have is a male. I didn't do any of the sexing of the fish, as I new nothing at the time, but now I am thinking I need to make some changes, and I am not sure what to change?
Any suggestions?
The males have a pointy anal fin called the genopodium and females have a fanned out sort of triangular anal fin...
...Also, I highly suggest not putting the female in a breeder net because it will stress her out and sometimes cause her to hold on to the babies longer than necessary, therefore sometimes killing the babies and herself along with it...the only time i ever put one of my livebearers in a breeding trap is when she is already in the process of dropping and the other fish are stressing her out too much by chasing and nipping at her...I know that the first time you have babies born in your tank it is really exciting, but let me just warn you, if you keep the babies alive, they breed like rabbits! And unless you separate them as soon as you can sex them, your tank will breed out of control! IMO, I would just let nature take its course...I didn't try to save any of mine and now I have 20! 
(which I will be separating as soon as I can tell if they are male or female)
