noticed at the morning feeding my ~10in oscar is bloated, has a small bladder out his backside and seems to have in his mouth also, my other oscar is freaking out but seeems fine, please help

50 gallon tank 2 oscars(both 1 1/2 old) and 1 sucker fish (5 years)

Sorry welcome you to the forum under such circumstances.

The first thing we need to address is your tank size. I'm afraid it's not think enough of a fish you've got. Second, have you tested the water for ammonia, nitrites, nitrates and pH? Because of the tank size, there is a chance that your water conditions might not be too good. By sucker fish, I assume you mean plec ? Some of these fish get very big.

Can you possibly take a photograph of your Oscar for us? I would like to see the extent of the swelling. As for what is sticking out of the fishes anus, it could possibly be part of the rectum/internal intestine, sometimes referred to as a prolapsed rectum. As for what is in the mouth, I really don't know at all. The only time I've ever seen strange things suddenly appear in fishes mouths is when you've caught fish at sea and the swim bladder has come up into the fishes mouth. I cannot see this happening in a fish tank though. Again, if you can get a photo.

Is the fish breathing heavily ?Has he gone off his food? I've got to be perfectly honest with you, I have seen this sort of thing so many times before. In fact, only last week was I reading up on somebody who had something almost identical on another forum. Unfortunately, the Oscar didn't survive. A swollen abdomen is unfortunately, not a good sign. It means something is going on inside the Oscar. It could be constipation which can sometimes be cleared up by feeding the fish peas. It could be cancer, it could be organ disease, internal bacteria/parasite infection. So you can see what we are dealing with, something that is virtually impossible to diagnose, and if you can't diagnose it, you can't treat it. You could try internal parasites/bacteria treatments. I doubt whether it will work. I had a tiger o a few years ago that had exactly the same thing, I tried everything but it still died in the end.

I'm really sorry but I can't help anymore. Just keep an eye on it, try it with peas just in case it is constipation. Apart from that, I can't really give you any advice that I may will help. I did hear somebody talking about Epsom salt bath, you could try that, again I doubt it will do anything but anything is worth a try.

As said your tank isnt big enough, and as a consequence your water quality is more than likely not good. What you need to do is test your water for ammonia, nitrite and nitrate. In the mean time give your filter a clean (use tank water to clean it) and do a 50% water change followed by a daily 25% water change. It doesnt look good for your bloated oscar although it may hopefully be constipation. If i was you i would add myxazin (its an anti-bacterial treatment) on the off chance. A word about feeding, only feed what your fish will eat in 2 or 3 mins and no more. As your fish are adults you can get quite easily feed once every 2 days. Good luck