Depends on the size if they are similar in size you should be fine. Just make sure that the retic is getting enough to eat cause the motoros are more agressive eaters and they may out compeat the retic for food.
Also motros get alot bigger than retics so do you plan on getting a bigger tank in the future for them. If not, I would suggest not getting them. Also the retic will need a bigger tank in the future as well. Just not as big as the motoros.