Hole in Corydoras belly

Hi! I made an account here just so I could get some help. I have a 3 cory cats in a 10 gal with my betta and they've been getting along great since my betta is pretty docile. They've been together for approximately 3 months. My tank has been running for around 2 years already and I consistently have normal readings from my API test kit.
I recently noticed that one of my cories was not playing with his other friends and was just sitting on the bottom. I took him out and put him in an examination container and he has a huge hole in his belly. It's a pretty clean, circular red hole and quite large.
My sand is very soft and none of my tank decorations could make such a clean hole so I know it's not an abrasion of some sort. I looked around on the Internet and apparently it might be a parasitic isopod??! If that's the case, should I euthanize him to limit the spread?
If anyone has any insight, please help me! I don't want my cory to die...

Here is an of the hole. HELP.

 

if it was me I would euthanize him. I am so sorry about your cory. And because I know someone else is going to say it Cory's shouldn't go in a ten gallon.

 

HI and welcome, sorry it's under these circumstances.

First of all, what are your exact water parameters?

A clean hole like that might also be from a burst abscess. Have you noticed any injuries on your other fish?

How are your cities behaving? Are they out foraging in the open or are they hiding a lot?

 

It's 3am right now so I don't have the exact parameters but I'm sure my tank is fully cycled. My other fish don't have any injuries and they're very active and eating like little pigs.
It's only that one Cory that's now hiding behind the driftwood...

Oh! Forgot to mention I'm treating the tank with melafix now. Yesterday I removed the carbon in my filter, did a 25% water change, and dosed for 10 gal.

 

What species are the Cories. Wildcaught or tankbred ?

 

What species are the Cories. Wildcaught or tankbred ?

They're tank bred. Bought them from Petco.

 

Welcome to the site! Water parameters will be a common question here as it helps give us some insight.

The only thing I can think of is that your Cory number is low 5+ and also that tank is too small for cories. These guys are super energetic and like to shoal around the tank.

 

Made me think of a parasite / isopod that got out a wildcaught Cory.. What Coryspecies is it ?

 

Made me think of a parasite / isopod that got out a wildcaught Cory.. What Coryspecies is it ?

It's a C. schwartzI I believe. Would I be able to see the parasite/isopod? What should I do?

Welcome to the site! Water parameters will be a common question here as it helps give us some insight.

The only thing I can think of is that your Cory number is low 5+ and also that tank is too small for cories. These guys are super energetic and like to shoal around the tank.

I will try to get my params up when I get home. I read somewhere that 3 was the minimum and that 10 gal was an okay size... Guess I was misinformed. I'll try to get them in a bigger tank eventually...

 

UPDATE: The cory has passed away. I performed a small autopsy and discovered his body was mostly hollow inside and that whatever has lived there (if it was a parasite) probably ate everything.

 

I will try to get my params up when I get home. I read somewhere that 3 was the minimum and that 10 gal was an okay size... Guess I was misinformed. I'll try to get them in a bigger tank eventually...

Yeah, people here generally say 20 gallon long and 6 cories minimum. So sorry about your Cory. It does sound like a parasite to me. Are your other fish acting normal still?

 

It's a C. schwartzI I believe. Would I be able to see the parasite/isopod? What should I do?

Then it probably is a wild caught one.
SchwarzI are rarely tankbred.

Sorry for you loss. I'd use a wormer and keep a good eye on your fish and tank.

 

Yeah, people here generally say 20 gallon long and 6 cories minimum. So sorry about your Cory. It does sound like a parasite to me. Are your other fish acting normal still?

Yes they are acting normal but I'm worried by a dark spot on their bellies (kind of where the hole was on the other cory)... I'm not sure about the anatomy of corydoras but from the pictures I've seen, most cories don't have a dark spot in that area.
Since I am unable to provide them the proper sized housing they need to thrive, I'm going to look into rehoming them. Blah I'm sad about that since they're such cute and amazing little fishes!

Then it probably is a wild caught one.
SchwarzI are rarely tankbred.

Sorry for you loss. I'd use a wormer and keep a good eye on your fish and tank.

Ah that's interesting to know. What wormer would you recommend to use that would be safe for my betta?

 

Ah that's interesting to know. What wormer would you recommend to use that would be safe for my betta?

Don't know the exact brands of wormer overthere (living in Holland myself).
In the UK KusurI is believed to be a good one. Don't know where you live though and about being Betta-compatible.