Ok, so I just set up my new 36 gallon tank, this is my first tank. I set everything up and ran the tank for a week before getting any fish. I bought 3 red long fin minor tetras on Monday. They adjusted fine for the first two days. Then started a problem. One is big, one small, and medium sized one that I believe is a female. The big one seems to be a bully, and now the middle one is not eating. It has not eaten in two days and now it hides alone behind the plants near the heater swimming in one spot. Is this fish stressed, sick, or bullied? Any help would be great!