Tough platty fry

[Wrongwill]

So I recently started my fist tank. 30. Gallonafter cycling with food plants and a small amount of seed media(gravel). I got 6 assorted plat ties. 2 died with in 24hrs. Waited 1 week replaced them. Everything in the tank was great. Pond snails, assorted plants, fish doing really well rose swords diddn't even loose colour(was warned this was likely due to my small 30 watt bulb)
3 days ago I saw a small redish fry. Set up to save him! After filling a bowl with water and a bit of plants I couldn't find himm anymore. Thought he was a Conner for sure. So I left the bowl full anyways. While doing a water change I spotted and managed to catch him last nite. So I bought a tank I will set up tonite as a nursery/hospital.
The water in the mean time in the bowl got cloudy! Thinking plant decay but only a .2 ammonia. So should I switch him to the tank right away or leave him in the 1 gallon bowl for a couple of days till the new tank is cycled(planning on stealing more plants gravel and filter juice from the big tank) so the new tank is only 3 gallons but does have a light filter and air stone.
Also being a live bearer fry will he be okay with crushed flakes and crushed brine shrimp?
Thanks for any help

First post though I have read and learned quite a bit over the last month

[Pamiam]

This is my 2 cents worth and Congrats on your little fry

When I have my fry, I use 50% water from the parent tank and 50% clean water at first. I never really worried about cycled water with fry. I would keep the air stone going for movement and oxygen exchange.

As for feeding I use flake food that has been crushed into powder form and some times I would hatch out brine shrimp.

I never used a filter until they were big enough to stay away from the suction. I have 20 day old cory fry and tried them with a filter yesterday, one got sucked in, so I stopped with the normal filter.

My set up since the day they hatched is they are in a 20 gallon, with an air stone and Aqua clear filter set to low suction and I covered the intake intake stem with a AquaClear Foam sponge that I cut a hole into to place the foam sponge over the intake steam.

The foam sponge gets dirty quickly so I rinse it out a couple of times a week.

[Wrongwill]

So the air stone was much too much for the little tank. So was the filter. Created a heck of a current. I blocked some of the out holes and put a denser sponge in and around the intake holes. I know this may shorten the life of the pump but that's ok. I can probably undo the modifications in a few days. Unless I get more fry two of my females in the larger tank seem to be squared off.

For the water I did as you suggested added 50/50 old tank new (primed) water.

I also put some snails and plant cuttings (some planted others floating to give Fry a hiddy place options. If the plants die off under the crappy little light that came with the tank that's also ok the big tank needs frequent trimming anyway.

I was hoping to stock more fish into the big tank this weekend. Few guppies(6) But now I will have to wait. How long until my Platty fry can go back with the adult fish? I know they grow fast he already has full colour though no mickey mouse tail and has probably doubled from when I first noticed him, but I don't know how long to separate him from the big tank for?

[Pamiam]

they can return to a community tank when they are big enough not to be eaten