Frozen bloodworms seems a favorite for most fish.
If you plan to use salt, make sure you dissolve it in water first, then slowly pour the solution in your tank under a long period of time. If you drop the crystals in the tank, the fish might think it's food and try to eat it. Even scaleless fish can survive aquarium salt, as long as it's diluted in water. I have clown loaches (scaleless fish) and they never seem to get bothered.
If your danios or zebra danios, I would watch them carefully or maybe move them out. I have heard of several occurrences that they can be fin nippers, especially towards angelfish. I guess I was fortunate with I had several zebra danios in my tank with 2 angelfish, because the angelfish were fine.
What type of filter do you have?