Red tail catfish suddenly died

  • We are currently upgrading MFK. thanks! -neo
I’d cut back on the feeding and increase ur water changes( more than once and large volumes). Make sure ur adding a dechlorinator. Recheck the water.
 
If you are rinsing the media in tap water chances are you are killing all the beneficial bacteria thus causing a mini cycle every time you clean the filter. You should use tank water to rinse the media. I have three canisters on my tank and rotate the cleaning so there are always two that have plenty of beneficial bacteria
 
are you sure i have had that happen to him before this was also on the catfish and appears to be coming from beneath the scales it is also on his eye

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This pic looks as if your Oscars lateral line is in some way "infected" for lack of a better terminology. As others have said you are causing recycles in your tank. Ammonia and nitrite are very toxic. Nitrate isn't as bad but elevated levels have been thought to contribute to hlle which Oscars are prone to getting. Poor water quality, bad diet, carbon use, stray voltage have also been thought to have some effect. In an case it is usually stress that allows the virus to infect the fish. Is your pond out doors? Have any of the items from the pond been in or out of this tank? Most out door pond have the virus according to recent studies. This doesn't mean all fish will develop hlle but if stress levels are high then it's is more likely. In any case if you have transferred anything between tank and pond other infectious organisms could have come along, with your tank constantly cycling your fishes immunity could have been compromised. How long have you had these fish?
 
Just got back to this thread after my initial response in #3. In that post I mentioned a lack of detail, we needed more info to give us a clearer picture as to what's going on.

And boy, that picture is becoming crystal clear as the thread goes on.

Those two fish have been living in an undersized torture chamber, made even more torturous every time you do a water change. It says a lot that one of the hardiest fish known in the hobby has finally died. And unfortunately your oscar is probably too far gone to pull through too. Very sad.

There are a lot of valuable lessons to take from this.

Housing fast growing fish in small tanks whilst you "work on their upgrade" is one of the common mistakes made. Life happens, you get side tracked, your upgrade gets shelved or put on the back burner etc etc.

You need a reliable method of checking your water parameters, on here most of us have the API liquid kit.

You've got to do water changes that equate to the bio load your stock is putting out, not just an amount that you think might suffice (your test kit will give you the answer to this).

And when you do perform water changes you have to look after the contents of your bio chamber in your filter like your fishes lives depend on it....BECAUSE THEIR LIVES DO DEPEND ON IT!!!!

I pray that your oscar makes it. Don't get too disheartened if it dosen't, just ensure that you learn from this and moving forward put measures in place to prevent a sad recurrence.

Good luck.
 
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