I would always add tons of plants instead of adding them to a breeder box. If you want to add something to the breeder box I would add the fry if you want to keep a close watch on them.
They could of eaten them. They are Livebearers they WILL eat your fry. I had a platy drop only one fry one time and there was plenty of hiding spots. 86 F is a little high. Platies aren't like guppies in my experience they don't have as much fry but they last longer which turns out to be more fry in the long run
In my 5 gallon I have 5 white clouds, 4 Pygmy Cories, and 8 Ghost shrimp. It's a really cheap and hardy stocking for a five gallon. After I added the plants everything ended up being about 40 dollars. SUPER CHEAP!
For the Cycling question I would definitely add a sponge filter from another tank and add some plants and it will basically instant cycle the tank. You could also just add a HOB filter cartridge and shake it around for about 3 minutes and it will instant cycle it too. Love to see some pics!
I have to say. My Golden Panchax killies are the MEANEST fish I've ever had. They bite me all the time when I am doing water changes. Even though it doesen't hurt it scares the Crap out of me. 😆
So I am setting up my spare 3 gallon tank and have been watching TONS of aquarium co-op nano videos. I really want to do something cheap and really cool. Thanks!