In either case you can dry marinate the fish briefly with a light blend of spices, you can brush it with a marinade of mirin, soy, and ginger if you're going to steam it (yummy with salmon or tuna), or if it's a fish that can stand up to more intense flavor you can use a blackening spice.

Fish in this variety include black sea bass (branzino), red snapper, and tilapia. Before placing your fish in the sous vide pouch, add a teaspoon of butter per fillet, your favorite herbs (dill and thinly sliced shallots work well). To finish, sear in butter or olive oil for around 30 seconds on each side.