The Red Fin Shark might get nippy at the Tetra (depends on personality). You can add him and see how he takes, if he gets
overly aggressive you will have to move him(may or may not be a him). I would try and find another home for the Bala
Shark as they get way to big for your tank (12-16 inches)and should kept in groups. So you decided on going for the traditional cycle with fish huh. What are your ammonia and nitrite readings? Did you have the Tetra in the tank for the whole cycle? If Yes It would be a good Idea to give all of them a Methylene Blue dip after the cycle is complete. The dip will help with the ammonia and nitrite poisoning that the fish suffer during cycling. Since you are "rescuing" the fish from some other tank it would be a good idea to give them a salt dip before adding them to the new tank. This dip is just precaution so you don't spread bacteria, parasites, and or other disease that may be present.