At this size the isopods should develop quickly and get a decent size. On the one hand I can recommend Armadillidium frontirostre to you. This species grows to a size of 2 cm and has a very good offspring rate, which also develops quickly. The other species is Porcellio laevis. I particularly recommend the orange color form, because it is better seen and also eaten.

The animals grow up to 2.3 cm and must therefore be fed before the adult size. The development times and the rate of offsprings are perfect for you. Another suitable species is the Armadillidium spec. “Albino”. The size of the adult animals is 1.7 cm and they also have the same good reproduction rate and development time as the previously described species.