weird RES behavior with fish
Hi, I'm new to this forum thing so be patient with me please...
My fiance and I have had our RES since June, and we got him / her when he/she was probably 3-inches across. We put some goldfish in the tank and he/she wouldn't eat any of them. they grew. big. we figured they were new friends and would just live together. 4 mo. later we upgraded to a larger tank, and suddenly in one day, he/she hunted 8 LARGE goldfish and ate them all! Is that normal? Also, I say "he/she" because when we got it, we were promised that it was a girl, but recently we've been flashed a big black thing coming out of its butt area a few times, and everything i read tells me its a penis?