One of my aquatic mini frogs is now twice the size of the other one, and very mean towards the little one?

i bought the frog o sphere from brookstone with the 2 aquatic mini frogs and i have had them for about 7 months and over time one of them grew a lot bigger, hesdefinitelyy twice the size of the other one. and when i feed them, the bigger one eats the food right away and i have even seen him bite the little one multiple times when it goes for the food. i don't really know much about them other then what the directions say so does anyone have experience with these frogs? i feel like one day the little one is just going to be gone because the big one ate him.. should i separate them?