Someone gave me a few rosey reds from a pond, I added them to some mosquito fish I caught in a lake that now live in a tank on my kitchen counter, I just noticed two of the five rosey reds with shredded fins. What would be the best thing to add to the tank to clear up this "stuff".

You will need to separate the fish. Mosquito fish can be very nippy. To help heal the rosy reds, treat them with aquarium salt (a tablespoon per 2 gallons) and MelaFix by Aquarium Pharmaceuticals. If there is signs of infection, add an antibiotic like Maracyn by Mardel. If it gets fuzzy, add a fungicide. Minor fin damage usually heals pretty well if the water quality is good, and the fish otherwise healthy. I suggest weekly 50% water changes in a large enough tank. Good luck!