Help My Oscar Is Dying

help my oscar is dying 
he has the fin rot 
water is normal 
but it hit a bacterial bloom 
ive started using aquarium salt and melafix 
my water is not clear 
what should i do to clear the water and make sure my oscar lives 
this a relatively new tank 
3 weeks old 
ive attached a photo of the oscar suffering 
and a oscar thats normal in the same tank 
 
they all normally live in a 55 gallon tank 
but my plant began to decay and i had a bacteria bloom in that one as well the water is clearing up though 
 
i recently added a new fish two weeks ago 
 
 

If your tank is only 3 weeks old and you added fish two weeks ago, how did you cycle your tank? You need readings of ammonia, nitrite and nitrate. The best option for the fish to live is to take them back to the shop straight away. I cannot tell from the picture the size of your oscars, but you have at least 3 in a 55g tank, which is not big enough. Its only just big enough for a single oscar.
 
If you do not wish to take them back to the shop you will have to treat the tank as doing a fish in cycle http/www.fishforums.net/index.php?/topic/224306-fish-in-cycling/but I strongly recommend you return them to the shop and carry out a fishless cycle. Oscars are too sensitive to take a fish in cycle.

I agree that you are likely dealing with an ammonia issue. You'll need to pick up a liquid test kit (if you haven't already), do a very large water change, and seriously consider rehoming the fish. Even if you decide to do a fish-in cycle, these guys will need a massive upgrade or they'll need new homes very quickly (if they survive a fish-in cycle).

attibones said:

I agree that you are likely dealing with an ammonia issue. You'll need to pick up a liquid test kit (if you haven't already), do a very large water change, and seriously consider rehoming the fish. Even if you decide to do a fish-in cycle, these guys will need a massive upgrade or they'll need new homes very quickly (if they survive a fish-in cycle).

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This is sound advice. 

Agreed with the above stated. Just remember, the normal rule for oscars is 75 gallons per oscar, so 150 for two and 225 for three, etc... And it looks like you have three or more in there, and these guys poop A LOT, so having them in an uncylced 55 gallon is certain death for them, even if you do daily water changes of 10-25% because this would cause a lot of stress on the fish, other wise i agree with everything stated above.

Bacterial blooms are, from experience, the resulting effect of very high ammonia readings. I would recommend you set up a separate body of water and place the fish into that body of water while you complete a 100% water change on your main aquarium. From then onwards I would reduce your fish stock and acquire some filter media from an established aquarium or pond which you can add to your main aquariums filtration system so that it is more able to lower your ammonia and nitrite waste.