Are the in the cichlid family, Larkin? I think they are a very pretty fish!
Shannon, the brackish fish aquarium can have some really cool fish in it, and it's pretty easy to keep, much easier than true salt water. I have mollies in my brackish with 2 green puffers, a mono and an archer. pretty cool looking set up. I have rocks from my pond project in the aquarium to make it look more natural, too. Mollies are typically tropical fresh water fish, but adapt very easily to brackish water. Just have to take longer to acclimate them. I have 3 blacks and 2 white mollies in the brackish aquarium.
Larkin, I didn't know platies or swordtails could go brackish! Wonder why my pet shop never mentioned that! I think they would rather I buy the more expensive brackish fish, I guess. LOL Someone on here said the mollies could work, and when I asked pet shop, they said, "Oh yeah, didn't we tell you that?" LOL
Shannon, as with pond water and any type of "kept" fish, make sure your water is cycled and has good bacterial up and growing in it before adding any fish. That's why I kept the water when I bought the 55 gal aquarium. Already cycled. There are also products to "jump start" your aquarium water. Good luck!