those arent the true yepenzi they are potr. sp (unammed rays) just letting you know because they get bigger then them think around 24" male 30" females and all you need to look out for is that motoros are agressive eaters so if they arnt eating very well i wouldnt introduce a motoro
I have peru yepezi and motoro at the same tank. They have quite the same behavior. the peru yepezi (humerosa ?) is even more active than the motoro's. He is very active and NEVER rests, though less agressive when it comes to food i.e. smaller mouth than that of a motoro - so, need to make sure he eats in a common tank, before everything is eaten.