Help Rescued Oscar W/ Hith


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Problem: A little over a week ago I rescued a 9" oscar with hole in the head, fin rot, and ammonia burns. He is currently in a 29G but I need recomendations for his tranfer into my 55G.

29G with 40G filter, heater (75°F), 1 large oscar (2yrs old), previous owner never cleaned gravel and did minimal water changes. During the transfer pretty much all of the sludge was washed away and I may have gona a little overboard, making the tank 'too' clean. 60% of the water was changed during the move and I have been lightly gravel vacuuming to gather waste during water changes leading up to now. He was only fed feeder fish with minimal substitutions to his diet that still weren't nutritional and is now eating hikari cichlid gold large pellets 2x a day, 3-8 pellets per feeding, along with occasional beefheart, bloodworms, crickets, and nightcrawlers.

Current treatment: I have been doing daily water changes (25-45%) and treated the tank with melafix for a week until I got general cure which I added today after adding carbon, waiting all day, doing a water change, and removing the carbon. The tank perameters are still way off... extremely high ammonia(>8.0) and nitrates(>200), a little bit of nitrites still(2.0), and fairly low pH(6.2) (not that low for an oscar though). I am using test strips and API freshwater master test kit. I was previously using seachem stability but heard a few horror stories and stopped using it. I just started adding aquarium salt, I added seachem neutral regulator, and continue to use water conditioner, along with the general cure mentioned above... I beleive I am on the right path however I'm open to any suggestions.

Help: So I have had a 55G aquarium set up and running for over a week, I added some water from my other fish tank to kickstart the Nitrogen cycle, and the parameters are pristine. I would really like to move Al (the Oscar) ASAP but I'm afraid he'll be shocked if I put him in the new tank despite it being waaaay better for his healing process. I hope this was enough background info, what do you guys recommend I do?



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More than 10 years
Welcome to Fishlore, we have quite a few Oscar keepers hope they will chime in & help you today


Fishlore Legend
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More than 10 years
Keep up slowly getting his tank clean. Once his parameters are pretty close to the 55 move him. It may take a month but slow and steady wins the race.


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Here are some very useful information on treating Hole in the head.

I agree with David.
If you keep changing the water in your 29G, the water parameter will be like the 55G soon.
Each time you change the water, you are actually diluting/reducing the ammonia, nitrite & nitrate.

If my theory/assumption is correct, here is the calculation:
[unless there is something that can cause the spike in ammonia, nitrite & nitrate that haven't been removed]

If you change 50% of water each time, you're diluting everything (ammonia, nitrite & nitrate) by half(1/2).
[multiply by 0.5 for each water change]
100% -> 50% -> 25% -> 12.5% -> 6.25% -> 3.125% -> 1.56%.

If you change 25% of water each time, you're diluting it by 1/4 each time.
[multiply by 0.75 for each water change]
100% -> 75% -> 56.25% -> 42.1875% -> 31.64% -> 23.73% -> 17.8% -> 13.34% -> 10%

Take note that adding some water from other tank won't really kick start the nitrogen.
The beneficial bacteria stays mostly in the filter media and not in the water.
You have to get the filter medias from other stable tank over to kick start the nitrogen cycle.

Are you still using the old filter medias for the 29G tank?
You must not overclean the filter medias as they hold the beneficial bacteria.
Else, you will have to restart the nitrogen cycle in the 29G tank.

You can remove/vaccum all the waste in the 29G tank that is contributing to the increase in ammonia, nitrite and nitrate but don't overclean the filter media.
Any rotting/decomposed stuff must be removed.

Also, don't overfeed your Oscar as it will increase the ammonia, nitrite and nitrate level especially when the ammonia level is out of control.
Reduce feeding to once a day.

Here is a good info about feeding Oscar:

For ammonia and nitrite poisoning, you can use Methylene blue. But you can only use it probably on the day when you're moving it over to the new 55G tank as Methylene blue will kill off the beneficial bacteria in your tank.
Or alternatively turn off/remove all filters when you add Methylene blue and make a large water change before turning on the filters.

Here is the info about Methylene blue.(Sorry, I'm unable to post the link here)
-> Methylene blue.

All the best!
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