Hello and welcome to FF! Appears your larger frog is a bully . A problem with a small tank is that there is no way to get away from the bully, and that could stress the victim and invite disease to the tank.

In a larger tank, you could use 2 feeding stations to avoid issue and add more hiding spots to break line of sight contact between the 2. Also, could introduce more frogs (after quarantine) so that bully either quits or divides bullying among more than one frog. Obviously separating these 2 is an option too. Hope this helps a bit and give you some ideas, good luck !