Best way to increase tetra size?

[Redeuckus]

My local aquarium store can only gets it very tiny tetras(1/4 inch or so). What is a good way for me to increase there size befor adding them to my main tank? I am worried they are small enough to be eaten by my other fish but I would like a nice shoal of tetras in my aquarium as dither fish.

[Aiken Drum]

Get a quarantine/grow out tank and keep them there until they are a size at which you are happy to transfer them to your main display tank.