I found this online:
Fish fry are often food
for other fish. And some fish eat their own young. To keep the little ones safe, relocate the adults to another tank after they've laid their eggs or released their fry.
Too much of a good thing can harm the fry. In a small tank, churning water can be dangerous to fragile fry.
2. How to Protect Baby Fish
There are two types of these contraptions available, and both fit inside aquariums. One such contraption is called an Aquarium Net Breeder, and it has a thin frame made of plastic that's covered with a fine net to separate the babies inside the net from the larger fish outside the net.
Click here to see a picture of two Aquarium Net Breeders that have been assembled and attached to an aquarium.
The second type of contraption is made of solid plastic and has an upper space for the female. There is a second space below and a slotted divider between the upper space and the lower space. The slots are small enough to keep the female out of the lower space, but big enough to allow the babies to fall through to the lower space, after the female releases them.
4. How to Make Powdered Food
for Baby Mollies and some other types of baby fish. Put 1 or 2 tablespoons of flake food in a plastic bag. Make sure the bag doesn't have too much air inside, then tightly seal the bag with a rubber band. Squeeze the bag between your fingers to mash the flakes inside the bag into a powder. It may take you 10 or 15 minutes to mash all the flakes into powder.
It's difficult to get a small amount of the powdered food out of the bag and into the aquarium. Here's another hint. Use a toothpick. Dip just the tip of the toothpick into the water. Then wipe the tip off with your finger, so it's just moist. Dip the moist toothpick into the powdered food in the plastic bag. A very small amount of the powder will stick to the end of the toothpick.
Just touch the tip of the toothpick to the surface of the water above the baby fish and watch them eat. They'll need several feedings each day. When your baby fish have grown to double their original length, they can usually be released from the breeding contraption into the aquarium with the other fish.
This method of preparing food for baby fish will produce a fine powder, that many baby fish can eat. But some baby fish are too small to eat this powder. For example, baby Angel Fish are too small to eat this powder.
Many newly hatched baby fish, like Angel Fish, are too small to eat this sort of powdered food and need to eat newly hatched baby brine shrimp for a few days, before they can start eating powdered food. Click here to learn more about baby brine shrimp.
Don’t be surprised to find the adult fish eating their young. To prevent this, be sure you have plenty of places for your fry to hide. Include plants, decorations, and rock crevices for their protection. You can also purchase a floating plastic “baby tank” for your fry, but personally I have not had any luck with these. Our babies have lived best swimming in the large fish tank with lots of places to retreat to if needed.
Fry should be fed a few times a day with ground fish flakes. After a few weeks you can feed them on an “adult” fish schedule. Again, be sure your tank is large enough to hold a school of baby fish… and remember, they will become as large as their mommies and daddies!
As with any livebearing fish, it is best to have at least 2-3 females per each male because male livebearers often harass the females. Plants are also good so that the females have plenty of hiding spaces.
Like any livebearing fish, platies are easy to breed in an aquarium. Spawning will occur in a community tank. All you really need to do is to put a male and female fish together. You can also interbreed them with swordtails (Xiphophorus helleri
It is sometimes difficult to tell when your female platy is pregnant. This is because not all female platys have a gravid spot. In the females that do have a gravid spot it tends to get larger as the fry grow larger.
Platy fry are born fully developed in approximately four weeks. There is no parental care of the fry. The parents may eat the fry and so it is best to separate the fry from the adults if you want them all to survive.
If you are unable to keep the fry separate, having lots of hornwort in your tank (both floating and planted) will help to protect the fry.
You can also use a breeding trap. These are inexpensive and are available at most pet stores. Breeding traps are plastic containers that you put the pregnant female in (or any livebearing fish). Don't put the female into the trap until she is close to giving birth. The breeding trap floats in the aquarium. The trap is separated into two compartments. The top compartment houses the pregnant female platy. There is a small space between the top and bottom compartments so that the fry drops through to the bottom compartment where their mother can't reach them. It is possible for the fry to swim back through this space into the top compartment, but they usually don't. After the female has finished giving birth to the fry you should remove her from the trap and place her back in the aquarium. The plastic piece that separates her from the fry should be removed from the trap and you can raise the fry for a short time in the trap. However, the water in the trap tends to get somewhat stagnant and so this isn't an ideal place to raise the fry for long. If you do raise the fry in the trap you will need to clean out the trap and replace it with water from the aquarium on a regular basis. It is best to raise the fry in their own aquarium. Because they are so small they can easily be raised for awhile in a 5-10 gallon tank of their own.
Keep in mind that female fish tend to find confinement to the breeding trap very stressful. If you have another aquarium it is best to place the female in it (and have no other fish present). Make sure it has lots of hornwort so the female fish won't eat her fry. As soon as she is finished giving birth to the fry, then you should place her back into the main aquarium. Then you have the fry in an aquarium of their own to raise them in.
Feeding the Fry
Platy fry can be fed newly hatched brine shrimp, newly hatched daphnia, or they can be fed powdered fry food for livebearing fish. You can find these online or at your pet store. I've successfully raised baby platies to adulthood using dried fry food, however, you are going to get better growth of your fry if you feed them live food as well as the dried food. Don't try to feed them flake food for adults because the fry are too small to eat them.
I have read a lot on what to put them in, and most people are suggesting a breeding net. Not sure if there are any LFS open around you right now, but I would get something ASAP and not leave the other fish in the bucket/other tank for too long. And it says to leave the babies in there for a month.