Oscar fish disease with white slime peeling off skin


please help me out. My Oscar fish isn’t eating since last two days. He has confined himself to corner and not interacting with other fish in the tank.

Have maintained tank temperature to 29 Celsius and added aquarium salt. Have used medicine that has turned aquarium water greenish.
Please help!


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Can you fill out the emergency template for us, please? There's lots of info on there that would be helpful in the diagnosis.

How much salt did you add, and which medication did you add?


Please find details mentioned below:

What is the water volume of the tank?
150 US Gallon
How long has the tank been running?
1 month
Does it have a filter?
Yes canister filter
Does it have a heater?
Yes 2 heater each of 200 watts
What is the water temperature?
28 Celsius
What is the entire stocking of this tank?
Oscar: 6
Severum: 5
Parrot: 2
Albino pacu : 2

How often do you change the water?
14 days
How much of the water do you change?
What do you use to treat your water?
SeaChem prime
Do you vacuum the substrate or just the water?
No substrate. Bare bottom
*Parameters - Very Important
Did you cycle your tank before adding fish?
What do you use to test the water?
What are your parameters? We need to know the exact numbers, not just “fine” or “safe”.
Ammonia: 0 ppm
Nitrite: 0 ppm
Nitrate: 10 ppm
pH: 8.4

How often do you feed your fish?
twice a day. One day no food in a week
How much do you feed your fish?
10 gms each time
What brand of food do you feed your fish?
Tetra bits and okiko platinum
Do you feed frozen?
Do you feed freeze-dried foods?

Illness & Symptoms
How long have you had this fish?
19 days
How long ago did you first notice these symptoms?
2 days
In a few words, can you explain the symptoms?
Fish is lathergic. Not taking food, staying isolated white lesions in skin as shared in picture.
Have you started any treatment for the illness?
Aquarium salt 800 gms. Trypafavine, aniline green oxalate, tetramethylthionine chloride(20 ml), SeaChem stress guard
Was your fish physically ill or injured upon purchase?
How has its behavior and appearance changed, if at all?
Fish is lathergic. Not taking food, staying isolated
Explain your emergency situation in detail.
(Please give a clear explanation of what is going on, include details from the beginning of the illness leading up to now)

Please help me out in treating him. He has been strongest among my other oscars and most senior.

Diane 007

Can you post a pic of the entire tank? You mentioned this tank has been set up for 1 month, is it cycled and how are you testing water parameters?


I’m kind of freaking out here.
Are we being trolled?

This is an overstocked tank IMO

It’s only been running one month and it’s only had two 30% water changes?

My fish would be dead.

I’m sorry. I had to edit my post a couple times because I said some very harsh things that may not be warranted.
When you start a tank, for the first month, I tell people: You can only put in one fish.

The biology has to get up to speed and that normally takes months in a 150.

Diane 007

I’m kind of freaking out here.
Are we being trolled?

This is an overstocked tank IMO
I agree about the stocking but it’s a new member and may not know.


I missread the OP post, and I thought it said 000. (In that case I would definitely advise someone else to test the water.)

Would this tank even be 0,0,10 after one month?

However, I have seen this slime drop off on my own Oscar immediately after a water change.

He recovered in two days. But his slime coat was affected by some very soft water that I added to his tank. I did not expect nor test for this. It was an accident. He just played in the stream & got well hosed with too-soft water.


Water parameter test using API KIT
RIGHT: nitrite
Middle: ammonia
Left: nitrate

please also find attached tank picture:

Please note that I had done initial cycling with mollies and guppies and got the water parameters ok where ammonia was 0 and nitrate around 2 ppm with nitrite


OK those fish are all quite small so far. Not overstocked, so now I am confused. Did you cycle this tank with guppies before the “one month” that we have discussed already?

I can’t tell a whole lot from the photographs but I would say change that water. I Keep my Oscar in a 125 with mollies, guppies, African cichlids, and assorted catfish. Of all of those he is the most sensitive to water quality.

Before any of the other fish show any symptoms of stress he will start to develop a little fuzz on one of his fins, and I know I am neglecting him.

His tank is part of a 200g cascade system, comprised of 4 vessels.

I am changing 100 gal per week.


Hi ulu,
I had cycled my tank initially with mollies and guppies. That’s true.
Today also I tested the water parameters. All look fine. I will also follow the trend of weekly water change of 30% but it’s winter now. Won’t there be any further stress if I change water because that lowers the water temperature by around 2 degree Celsius?
And good news is that my Oscar is recovering well and socialising much better than before. Again thanks for all
Another query! How often should I turn on my canister filter’s uv? Is it required please suggest!


When should I make water change now?
Should I wait till full recovery of my Oscar fish(taking feed)?
Please suggest what is to be done
my filters are on now. Should they be on during the treatment. Please suggest!


These are my suggestions.

I think your Oscar’s stress was all due to water change practices. I’m not certain what exactly was done wrong. Did he swim through a stream a of very warm water? Water warmer than the human body? This would cause the slime to shed.

Also, any contact with a more acidic (very soft) water than what he is used to will cause the slime to shed.

I suggest you change the water twice as much as you’re doing it now, but make sure the tank water temperature never changes more than 1°C. In any event temperature changes in the tank should be done slowly.

If the filter isn’t clogged don’t clean it. Let it age and add probiotics to the filter. I like Bio-clean. I use it every week.

There’s nothing wrong with the stuff that you are using and people I trust consider it safe for almost everything.

I haven’t tried Bio-clean with everything, but I have various snails, Guppies, Mollys, Oscars, various African cichlids, cories and assorted catfish.

I also keep a brackish system with mono sebae in it. So far it has been nothing but wonderful.

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