What do my Platy fry eat?

Okay, so I bought a female platy who was super pregnant, it turns out, and must have given birth last night because her gravid spot has faded back to normal and she is almost as thin as the males all of a sudden.
so that means...Fry! Loose in the tank with three adult guppies and three adult platys and one bladder snail.
they have lots of places to hide among the rocks at the bottom of my tank and among the wisteria. A 'breeder box' is coming in the post tomorrow or the day after, and I plan on going on a grand fry hunt, to capture them all and put them in this mesh cage in the tank with the adults, but protected.
But...what do they eat? Do they eat the algae in the tank? I feed my adults plenty of food (but not too much) so they are less hungry for baby fish, (which, by the way, I haven't seen) but what do the babies eat?
PS: I can't get ahold of live food.
Help! What do my platy fry eat?!

 

Update: I saw two fry this morning! A yellow one and an orange one. I put in a container, with holes big enough for the fry but not big enough for the adults. Is there anything else I should do? When the pen comes, I plan to clean out the aquarium, and capture as many fry as I can find and put them in the pen, but leave the container just in case I miss some.
From the size of my platy when she was pregnant and the size of the fry, I would say there are about 5-10.
WHAT DO THEY EAT?!

 

Yesterday I cleaned out the aquarium and captured OVER THIRTY platy fry! (I accidentally killed two :eek They are in a honey container with holes until their breeder box arrives in the post this coming week. They are all orange/yellow variants.

 

What are you going to do with them? That's the problem with livebearers (and I love them).

 

I hope to sell them to a pet-shop or online.

I am also expecting a batch of guppy fry any day to a couple of weeks from now.

 

you can feed the fry this Amazon.com : Ocean Nutrition Instant Baby Brine Shrimp 0.7-Ounces (20 Grams) Jar : Pet Food : Pet Supplies I ordered it from amazon.com for my fry or you can just crush up pellets or flakes into a fine powder and feed that too them

 

you can feed the fry this(pictured below)I ordered it from amazon.com for my fry or you can just crush up pellets or flakes into a fine powder and feed that too them

Thanks! I think I saw this in my pet-shop. I will try to get hold of it!

 

For my guppy fry I just give them the powdery bits in the bottom of my jar of tropical flakes—you don't need to get fancy unless you want to! : )