I don’t think you will find a place to buy redfish very easily. If your pond has forage enough to handle a nice sized redfish you might have to embark on a fishing adventure. Take a cooler or live well with you. Catch one from the wild and relocate it. Be aware you might have a size minimum length and possession limit to be concerned with. You could stock a couple 18-25 inch reds or what ever you can keep or catch.
They are hardy and transports well, just make sure you have an aerator in your live well or cooler.
They are really easy to acclimate over. I drain about half way down and refill by letting a well water hose drizzle to slowly fill back up. Repeat this a few times and you should be at or near fresh water.
On the last time I use water from the pond, I guess you could use fresh water from the pond right from the get go.
All you really need to do is slowly keep adding fresh water to gradually take the salinity to the level of the pond.
If you fish and catch jack Crevelle, Southern Founder, Mangrove Snapper, Tarpon or Snook you could do the same.

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