What's wrong with my Oscar?

[petspoiler]

what are you "proving"? whatever it is, it's NOT diagnostics.

the point is to use the process of elimination until, hopefully, your oscar improves. sometimes a certain fish FEELS intimidated by the stare and/or body language of others. the mere fact of your O being outnumbered by a whole group of convicts might be uncomfortable for him. maybe not another oscar, but it's your job to find out.
the only way to do that is to CHANGE things and see if he gets better.
he doesn't look strong right now. if sticking to your assessment is your first priority, then medicate him in that tank (with the cons) for internal parasites and see if he survives.
Another issue is: there could be more than one thing wrong.
For instance:
(1). Water parameters.
(2). Tankmates are a bad fit for him.
(3). Internal parasites.

stress affects the immune system. and various health issues can hit simultaneously just by coincidence anyway. Combining issues in one fish, gets what you are showing in that photo of your fish.

 

[Miguel]

As you state Barbara, stress is the main door to all kinds of nasty situations/ diseases

 

[petspoiler]

and ps; it's a bad idea to medicate him in a weakened condition without trying to support him in other ways first.
if you don't have another tank to move the cons to, put them in a big rubbermaid bin with sponge filter & heat, to see if the oscar starts moving around more & eating.

 

[petspoiler]

true, Miguel. "I" am starting to feel stressed now. Lol.

 

[PwNz I R COLE]

He's stressed out look at his eyes the popping out of his head from stress


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[petspoiler]

I recommend moving the convicts, NOT the oscar. a new tank is stressful for oscars, even a good move, to some extent.
If he was in top form, that'd be different.

 

[probassfisher010]

Your water is toxic, probably because your tank is under filtered, especially in the bio department. What's your filtration?


And to those saying nitrates over 20ppm warrant a large water change immediately, your crazy.


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[00kevin]

I have a fluval 305 loaded with sponges and media. I've always felt confident with the filtration on this tank.

 

[probassfisher010]

One canister is not enough for your bio load. Add a new filter, ac110 with a sponge and the rest with biomax should be enough. Do a water change, add some seachem stability...At least thats what I would do.


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[dragonfish]

Have to agree with everyone on the convicts being the issue. Had a pair in the 120, smallest things in the tank. When they paired off and spawned they took over one end and no one got near, not the 8 inch oscar or the two foot fire eel nor anyone in between. WHen the wigglers became free swimming dad would take them for a swim around the tank chasing away all threats. Your oscar has no place to hide and looks like no other tank mates to take some of the bullying. They may have been ok before but if the convicts have started to mature it gets ugly very quick.