I set my tank 2 years ago. In 450 liters aquarium lived 4 oscars (about 28 centimeters length) and 2 red parrots (about 15 cm length) and some catfish. Outside Filter JBL 500 1200 liter/hour, inside mechanicel filter 800liter/hour.; temp.+25C. Parameters are good: Ammonia= 0 ; Nitrite= 0 ; Nitrate=10. I do water changes every 7-10 days about 15-20%.

2 mounth ago 1 my oscar started gasping and stoped eating (They eat Hikari food). Bacame sad and apathetic to everything. Abnormally strong gill activity was too. First of all I used medicament JBL Furinol - nothing has hapend, then JBL Gyrodactol against Gill warms- NOTHING! This state continue 3 weeks untill my oscar died. I thought that it was some very difficult to diagnose disease. But after 2 weeks my second oscar became the same condition- started breathing heavily and stoped eating. 10 days ago I did salt procedure 3 grams in to 1 liter water. After 2 days in salt water fish became very bad. Was gasping and lying on the ground. Then I changed the 40 % of water and put un-bacterial medicament called " Supplin ". Then I saw a little miracle MY OSCAR ate a little. But today is the 5 day that he is swim aapathetic with strong gill activity and don't eat any thing. I DON'T KNOW WHAT TO DO? WHAT medicine TO USE? PLEASE HELP!

Thanks, Oskaras

so your water is okay, ammonia and nitrite zero and nitrates at an acceptable level? You are absolutely sure?

I assume that all the other fish in the tank are okay? If there is a serious problem with the whole tank, all of the fish would probably be showing signs of ill-health, if it's just one fish, then we can pretty much narrow it down to that one fish being ill. As to what is wrong with it, that is a very difficult question to answer. How are the oxygen levels in the tank? Try increasing oxygen and see what happens.

Like I said, poor water quality often has a lot to do with fish health so you have to be 100% sure that your water quality is good. Unfortunately, fish often have internal problems that are absolutely impossible to diagnose until they have died and you can have them examined internally. I would suggest having a word with a vet and see what he has to say. Unfortunately we are not going to be able to help you, I wish I could but I would just be guessing. Fish can suffer from a wide diversity of illnesses so you can understand how difficult it is to diagnose, especially over the Internet.

It is difficult to say what is wrong with your fish

Has your water quality always been good. Long term exposure to high nitrates can lead to long term health problem that are difficult to treat

I checked water parameters every day and they are ideal. I increased oxygen level more. Raised temperature form 25/26 C to 29C and add suplin (un-bacterial preparat). Then after 2 days the fish helf became poor. Oscar started breathing more heavy and the stomach inflated a bit. Yesterday chaged 20 % water and lowered temperature to 26C and today the stomach have a bit lessen but still not like others oscars. The fish mood rised a bit.
The inmate eats only 3 days period some crumbs and swim sad around aquarium. Today i saw his atack against the other oscar and this maked me a big happy.
The other fish helf did't changed, maybe the other oscars breathing became more active.

I checked water parameters every day and they are ideal. I increased oxygen level more. Raised temperature form 25/26 C to 29C and add suplin (un-bacterial preparat). Then after 2 days the fish helf became poor. Oscar started breathing more heavy and the stomach inflated a bit. Yesterday chaged 20 % water and lowered temperature to 26C and today the stomach have a bit lessen but still not like others oscars. The fish mood rised a bit.
The inmate eats only 3 days period some crumbs and swim sad around aquarium. Today i saw his atack against the other oscar and this maked me a big happy.
The other fish helf did't changed, maybe the other oscars breathing became more active.

Help I need to know quick! I got home today and I went to check on my oscar and he was breathing hard and lying on the bottom! Help!!!!!! is he sick!!!!!!!!!!! Need to know now! help!!!!!!!!!!!!!!!!!!!!!