Hi,my oscar is in a terrible position. she is not eating since 3 weeks, and her belly start to become bigger an bigger. I have change my water in tank 2 weeks ago,since now my angel and some cyclide pass away. please help me. thanks!

Welcome to Oscar fish lover and I am very sorry that you have come to the website under these circumstances.

Okay, we need some information please. What size tank have you got? Also, we need some water test results, ammonia, nitrites, nitrates and pH.

Is your fish breathing heavily ?

Have you tried feeding? Does your fish just ignore the food?

How severe is the swelling? does it look like the Oscar has swallowed a ball?

Sorry for all the questions, I have seen this many times before. It could well be something like constipation, this can cause the swelling. However, it could be very serious unfortunately, there is a possibility it is either an internal bacteria infection, or an internal parasitic infection. You could possibly try treating the tank with an internal bacteria infection medication. However, I doubt whether this would work.

Could you possibly post a photograph of your fish?

Okay, it is vitally important you give us some water test results as possible and try and answer all the questions I've asked