Yes, you can legally keep these fish in America.
You got 14 Rhadinocentrus ornatus from a feeder tank in the US. Someone is gonna get their ass kicked for that. How much did you pay for them?
I know people in the US that spend years trying to get those fish so you need to breed them and sell the young.
Rainbowfish are serial egg scatterers, meaning they scatter a few eggs each day for a period of time, usually several months. The eggs are laid in plants or spawning mops and take about 1 week to hatch. The baby fish are fed on green water, infusoria, boiled egg yolk or powdered fry food for egg layers. The following link has information on culturing live food for baby fish.
https://www.fishforums.net/threads/back-to-basics-when-breeding-fish.448304/
To get the best results when breeding rainbowfish, feed the adults 3-5 times per day with a variety of foods. Do big daily water changes to keep the water clean during this time. After a couple of weeks of good food, separate males and females for 4 days, then put them together in a tank with some Java Moss or a couple of spawning mops. Spawning mops are made from acrylic yarn and put in the tank to collect eggs.
After 3-4 days, or even each day, you take the plant/ mop out and put it in a hatching tank and put a clean mop/ plant in the tank to receive more eggs. Do this for the next few months and you will get hundreds of young fish that you can sell. And you want to breed these fish because they are very uncommon in the USA.
If you don't want to breed them for that long, you can also separate the males and females for 4 days and then put them together in a tank with plants. Put the females in first and add the males a couple of hours later. Leave them together for a 2-7 days and then remove the adults. The following day you should see babies swimming around just under the surface.
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They don't live in seawater and are a freshwater fish.
You can use small amounts of salt to treat them for diseases but only use salt if they have a disease. They are normally pretty hardy tho and as long as the tank gets regular water changes and gravel cleaning, and the filter is cleaned at least once a month (preferably every 2 weeks), they should live for years.