I know first hand that motoros are hardier then retics. I had a very healthy retic for months and then I got a good deal on very sickly motoro so I bought her in hopes of saving her. Well about two weeks later my motoro was gaining weight and doing really good all the while my retic stayed healthy. Well one day I was doing a water change and I did not know it but my tap had an ammonia spike and to make a long story short my healthy retic died five days later while my motoro never even stressed!