Last night I came home to a very ill Boo (my catfish). I had known something was up with him, although he often got pale or stressed out, he did not greet me like he normally did when I got home and was hiding from me. I tapped the glass to get a reaction from him but he didnt move. My husband was able to get him to move a bit but not much. We thought he was fine just was tired. 10 minutes later he began swimming around the tank fast. Way too fast. He had his color back though, I just thought he was really anxious but didnt know why. He was splashing at the top of the tank. And then went back to crazy. I walked over to check on him and he just fainted. I dont know if fish can faint but he stopped and just floated to the bottom. I automattically panicked took him out of the tank away from the others (I have a dalmation molly, who loves Boo, two guppies, and two African dwarf frogs). Another side note. No one has ever had any problem with each other. I have had them all except the baby african dwarf frog now for a few months before everything closed because of COVID. Everyone got along just fine. Anyway, i took Boo out of the tank into my travel one to figure out why he fainted. He wasnt moving much and was breathing lightly. I noticed that he was starting to internally bleed or bruise. It was very red. I panicked more. He had a fight in him but he didnt make it. We lost him within the hour of the internal abdminal bleeding. The very odd thing is that he had started the splashing weeks prior. However he moved too quick for me to ever see him do it. I didnt know who was doing it at the time until last night and I saw it happen. When he fainted he had no sign of internal bruising or bleeding. He was his normal color. It took about a minute for the blood to get to the surface. I didnt know what to do. Or how to help him. He was the first catfish I ever had. I have learned a few things about his species that I never knew until now. I know that they usually are meant to be in schools but him and the dalmation molly where about the same size and grew up together in the tank through the course of the months that I have had them and were even brought home together. My dalmation molly is looking for his friend now and I really need to know what happened to Boo. It was very sudden. His attittude changed within the last week, I look back on maybe he was hurting. I have no idea. Here is what i do know. The tank water is perfectly fine. I tested it after Boo passed fearing that it was nitrate or ammonia posioning and my other fish were in trouble. But the water was fine. Boo had no bites on his fin and was perfectly fine on the outside. He has always been one to get pale, and when I noticed I always tried to calm him down cause I have read it is a sign of stess. Any information can help. I cant find any videos of what happened to him. Someone has had to have this happen before. There has to be an explanation. He was only about a year old. I have read too many things of what it could be but there was always a factor that eliminated Boo from it being what led him to death. No other fish are presenting any of the signs Boo was at all.