First off, congratulations on your first kids!
Putting them in a breeder net is probably your best bet, if you want to insure their survival. Leaving them in the tank is also an option, this is commonly called 'survival of the fittest'. Not as many babies tend to survive there, because you have the other fish that are trying to get a quick snack. There are pros and cons for each.
Breeder Net:
Pros:
- You can keep a close eye on them, and watch them grow.
- You can make sure they are getting fed.
- You can regulate how much, and what they get fed.
- You don't have to worry about the other fish eating them.
Cons:
- They can only stay in there for a couple of weeks.
Survival of the fittest:
Pros:
- You tend to get less fry, which can be useful, since Platies are fry machines.
- You get only the strongest, fittest fry (And probably the luckiest ones too!).
- You don't risk the chance of stunting or slowing their growth by keeping them in the breeder net too long.
Cons:
- You can't make sure they are getting food. Most of them will pick off little bits of food from the gravel, plants...anywhere they can find it. But some people like to make sure they are getting fed.
- You, of course, don't end up with as many fry.
There's also another option, the fry tank, which is the best of them all. Since you don't have one set-up, and it'd need to cycle before you could put any fry in there. It's something worth thinking about though, for the next batch. I wrote an article on that
here.
Anyway, as you can see, it's all personal choice. It's totally up to you.
If you
do put them in the breeder net, you'll want to feed them 4-6 times per day, if possible. Fry have smaller stomachs then adults, so they can't eat as much, and it goes through them faster. Common foods to start them off on is finely crushed flakes, fry food, or Liquifry. Liquifry can be hard to feed, so I'd go for either the fry food or the flakes. Once they get past the
really tiny stage (Usually about a week or so) then you can start giving them more variety. A balanced diet is best. So it's good to have some high-protein foods in there (Live, Frozen or Freeze-dried), and some veggies too. You just don't want to overfeed on the High-protein foods, because it can cause them to become constipated or bloated. Once a day should be fine until they can handle it a little easier.
There are lots of good topics on fry on the top of the Livebearer Forum, and also in the FAQ under Livebearers. I suggest you check those out, if you want more information. And of course, always feel free to ask questions!
Best of luck with the fry!