It's nice having them in separate tanks. But I just wanted to point out that green frogs will also eat other frogs. They are similar to bullfrogs in that they will try to eat anything that moves no matter if it's another frog. I keep both bullfrogs and green frogs.

The aggression you saw was not just because the other frog was a different kind. During feeding they get very excited and will lunge at anything that moves. They will bully each other. Bite each other on mistake. As long as they are relatively the same size however they have never tried to actually eat each other. They will fight over crickets. I normally feed them separately to avoid this.

Also if you ever get another frog be it either green frog on bullfrog they will sometimes bully each other without any food involved. I have one big male green frog that has claimed the entire shelf thing I built for them to sit on. If any of the other two green frogs attempt to get up there while he is there, he will push them off.

For me it is the opposite when it comes to temperament between green frogs and bullfrogs. All three of my bullfrogs are shy (unless it's feeding time). They hide all the time. They will only come out at night if they think I'm asleep. My green frogs can be seen out any time during the night or day and are not shy at all. They always think I'm going to be feeding them and will even jump into my hand thinking I have food.

As for croaking, that has nothing to do with aggression. My bullfrogs and green frogs do it all the time. They have several different types of calls. They even making little sounds when they eat. Even females croak. However they have different croaks than the males and usually do it less frequently. They do not do the typical mating calls either. So when sexing, sound isn't a very good indicator unless you are familiar with the various calls they do. I always go by how big the frogs tympanic membrane is to sex. On a male they are huge and there is no doubt if it's a male or female lol. As a juvie it can be a little harder to tell the difference in size.

Here is a male and female comparison and you can also see their ridges very well in case you might have any doubts about if you have a green frogs vs. a bullfrog.

Male:


Female: