introducing calvus to my frontosa tank

[elirix]

I've got a 125-gallon tank with seven frontosa and two calvus, two of the fronts are about 2 years old, the rest are a year. I'm looking to add more calvus, but I'm worried the fronts might see them as a snack. If the new calvus are decent-sized, the fronts should leave them alone. Does anyone know of a good mail order company that sells fish that aren't just tiny?