Red dot on corydoras belly

Hello everyone,

I just noticed today that my cory was acting strange. At first, he was sitting at the bottom of the tank for quite awhile without moving, and then he began to swim oddly around the tank and kept going to the top of the tank for air. That's when I noticed he has a red dot on his belly and nowhere else. With that said, all of my other fish are acting fine.

After doing some research, it sounds like a bacterial infection. Is there anything I can do to treat him or ease his discomfort? Also, it said bacterial infections often are from poor water conditions but I do a 25% water change each week and vacuum the sand, and my ammonia alert reads safe levels.

Thank you

We need a photo of this if you can. And, what is the substrate material?

Also, can you post the water parameters, which refers to GH, pH and temperature.

And, can you test for ammnia, nitrite and nitrate, and if yes, what are those numbers?

Byron said:

We need a photo of this if you can. And, what is the substrate material?

Also, can you post the water parameters, which refers to GH, pH and temperature.

And, can you test for ammnia, nitrite and nitrate, and if yes, what are those numbers?

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Substrate material is fine sand. My ammonia is 0, nitrite is 0, pH is 7.4 and GH 143.2.
I managed to get a very blurry picture of the corys belly, he’s spending a lot of time on the sand and his gills are pumping really quickly as compared to the other corys.

OK, thanks. I would venture to suggest that this might be red blotch condition. Photos similar to this one have appeared on Corydoras World and Ian Fuller has suggested this as the issue. I've no experience so I just offer this for your information, you can see what other members think. Here is Ian's file on this issue.

Treating ‘Red Blotch Condition’in Corydoradinae

Red blotch is a condition not a disease, secondary infection can and will exacerbate the problem.The most common cause of this condition is a sudden deterioration of the water conditions, i.e. Ammonia, or more likely Nitrite spike. The condition may take 24 hours or a little longer to show in a fish, and in that time the filter system may well have over come it and the condition of the fish is spotted the water can and is often back to normal, but the damage has been done.

The condition is not contagious, and each specimen within a group will have differing resistance to it.Red blotch condition needs to be treated as soon as it is spotted, as any delay will be fatal..

1. Large water change at least 50% if not more. If kept in a species only tank I would recommend a 75%+ water change.
2. Full dose of Melafix.
3. Add extra air stone with fairly strong flow.

It is also highly probable that this condition affects other armoured Catfishes groups, although I have neither experienced it or treated for it. Nitrite is also responsible for what is know as "Brown blood" again not a disease but a condition, and this is the result of a high level of exposure to Nitrite, which affects the blood ability to absorb oxygen. The gillsof fish suffering with this condition will be a brownish colour, instead of a nice pinkish red. Sometimes this can be fatal, but generally if good water conditions are maintained, over time the fish will recover.

Ian Fuller

can we get a clear picture of the fish?

Thank you everyone. I’m going to try and get a clear picture today.
HOWEVER...another one of my corys, who I had no idea was even sick, died this morning I didn’t even think to take his picture until after I buried him. His gills looked a little reddish. He was acting perfectly fine yesterday.

Do you guys think this is a bacterial infection? I’m going to try and get a better picture of my other Cory, he’s been sitting at the bottom of the tank a lot and not moving so I can get his belly.

I have hornwort in my tank but my pleco has been digging it up and destroying it and therefore; there’s a good amount of dead hornwort debris on the bottom of the tank. Do you think this could be harboring bacteria and causing my corys to become sick?

If I see red gills, I think of Ammonia poisoning. What are your Ammonia readings?

PheonixKingZ said:

If I see red gills, I think of Ammonia poisoning. What are your Ammonia readings?

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Readings of ammonia are 0.

Is there any sharp decor in the tank, that could have scratched its gills before it died?

(By the way, when was the last time you actually tested the Ammonia in your tank?)

PheonixKingZ said:

Is there any sharp decor in the tank, that could have scratched its gills before it died?

(By the way, when was the last time you actually tested the Ammonia in your tank?)

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I tested it yesterday and my ammonia alert also says it’s at 0.
I do not have any sharp decor but I do have hornwort debris on the bottom of the tank, do you think this could be the cause? I might just need to get rid of my hornwort and clean the debris.

I got a good picture of the Cory with the red dot on his belly.

Hokieokieamy said:

I tested it yesterday and my ammonia alert also says it’s at 0.
I do not have any sharp decor but I do have hornwort debris on the bottom of the tank, do you think this could be the cause? I might just need to get rid of my hornwort and clean the debris.

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Is the hornwort falling apart? I seriously doubt that the plant had anything to do with the death of your fish.

PheonixKingZ said:

Is the hornwort falling apart? I seriously doubt that the plant had anything to do with the death of your fish.

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Yeah it is, my pleco is de-rooting it and it’s causing debris on the bottom of my tank, which makes me think it could be sharp for the corys and may also harbor bacteria

Hokieokieamy said:

Yeah it is, my pleco is de-rooting it and it’s causing debris on the bottom of my tank, which makes me think it could be sharp for the corys and may also harbor bacteria

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It is possible...

Try to remove as much of it as you can. If it’s not growing as it should, it’s hindering, not helping.

I also suggest doing a water change. (40%+)

PheonixKingZ said:

It is possible...

Try to remove as much of it as you can. If it’s not growing as it should, it’s hindering, not helping.

I also suggest doing a water change. (40%+)

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Alright, I will do that. Thank you.