Peppered Cories suddenly mass-dying within a month.

[Sgooosh]

Hello, about a year ago, I purchased 6 very big peppered cories from my LFS, and suddenly, they are all dying.
I think there is only around 1 or 2 left from that batch. water has been the same, Wondering if it's age or something since they were very old when purchased and also no other fish have any bad symptoms.

 

[Sgooosh]

 

[Sgooosh]

I think I may have found the issue, the temperature is too high, the tank is at 78-80 f, which I've never set it this high before in spring/winter.
In summer it easily gets to more than 80, but I will lower the temperature and see how they do.
Does anyone have experience with this?

 

[GaryE]

I have experience with die offs, but who knows if they were the same thing. My last Cory die off were concolor I'd had for several months, and they turned out to have a colourless nematode that probably was the culprit. They died over a 3 week period with no external signs. I've had die off with newly purchased fish though, either from shipping ammonia or bacterial infections.
The body armour hides a lot, and makes diagnosing Corys difficult.

C paleatus became a hobby staple when heaters weren't available. It's an old timer, and it likes its cool oxygenated water. You can stress it by keeping it too warm. For a short time, surface air keeps them going, but the stress leads to illness. Their natural temperature range is 18-23c, and that should be in water that is filtered so that it makes the plants wave at you.

I keep Corys like that at around 22c. I'm learning the dynamics of my newish fishroom, and it's warmer than I like. I had a small group of Scleromystax barbatus that didn't make it though the warmth last summer when I was away in Gabon - they are like paleatus for their temperature needs.

For me, the dead of summer when tank temps creep up is a difficult time. I watch my Corys closely, and watch my water change routine even more closely.

 

[Colin_T]

Pictures of the remaining fish?

All Corydoras can tolerate a few months in 26-28C water. My Corydoras would be in 30C water right through summer and never had any issues with the heat. The rest of the year the temp dropped and in winter sat on 18C.

 

[Sgooosh]

I have experience with die offs, but who knows if they were the same thing. My last Cory die off were concolor I'd had for several months, and they turned out to have a colourless nematode that probably was the culprit. They died over a 3 week period with no external signs. I've had die off with newly purchased fish though, either from shipping ammonia or bacterial infections.
The body armour hides a lot, and makes diagnosing Corys difficult.

C paleatus became a hobby staple when heaters weren't available. It's an old timer, and it likes its cool oxygenated water. You can stress it by keeping it too warm. For a short time, surface air keeps them going, but the stress leads to illness. Their natural temperature range is 18-23c, and that should be in water that is filtered so that it makes the plants wave at you.

I keep Corys like that at around 22c. I'm learning the dynamics of my newish fishroom, and it's warmer than I like. I had a small group of Scleromystax barbatus that didn't make it though the warmth last summer when I was away in Gabon - they are like paleatus for their temperature needs.

For me, the dead of summer when tank temps creep up is a difficult time. I watch my Corys closely, and watch my water change routine even more closely.

Pictures of the remaining fish?

All Corydoras can tolerate a few months in 26-28C water. My Corydoras would be in 30C water right through summer and never had any issues with the heat. The rest of the year the temp dropped and in winter sat on 18C.

Thank you for your replies! I’ll get some pictures once I return home. My cories also go to around 80-90 f in summer without any problem, but I feel like maybe the change of season wasn’t as apparent this year specifically so they got stressed?
The strange thing is, only fish from that specific batch died. I don’t know much about them, other than they were very big when purchased. I have 1 other big peppered cory who has a dent in his head(seperate purchase) and 2 smaller ones from that batch left.
I have anaeus corydoras for a long time and none of them have any problems.

Some updates,
I turned off the heater (it is warming up here) so the remaining can feel cooler, and I’ll do a large water change for some fresh cool water

should I deworm everyone just in case? would you recommend prazi, metro, or flubendazole for soaking in bloodworms?

 

[Colin_T]

Intestinal worms don't kill a lot of fish suddenly. However, if you haven't treated those fish for worms, you can do them but do all your tanks at the same time to prevent cross contamination afterwards.

Don't use metronidazole, it's an antibiotic that treat internal protozoan infections and doesn't do anything to worms.

Flubendazole treats all sorts of worms and is good if you can get it but it kills shrimp so move them out of the tank if you have any. It might kill snails too.

Praziquantel only kills tapeworm.

Section 3 of the following link has info on deworming fish.

What to do if your fish has Stringy White Poop.

Fish do a stringy white poop for several reasons. 1) Internal Bacterial Infections causes the fish to stop eating, swell up like a balloon, breath heavily at the surface or near a filter outlet, do stringy white poop, and die within 24-48 hours of showing these symptoms. This cannot normally be...

www.fishforums.net

 

[Sgooosh]

Intestinal worms don't kill a lot of fish suddenly. However, if you haven't treated those fish for worms, you can do them but do all your tanks at the same time to prevent cross contamination afterwards.

Don't use metronidazole, it's an antibiotic that treat internal protozoan infections and doesn't do anything to worms.

Flubendazole treats all sorts of worms and is good if you can get it but it kills shrimp so move them out of the tank if you have any. It might kill snails too.

Praziquantel only kills tapeworm.

Section 3 of the following link has info on deworming fish.

What to do if your fish has Stringy White Poop.

Fish do a stringy white poop for several reasons. 1) Internal Bacterial Infections causes the fish to stop eating, swell up like a balloon, breath heavily at the surface or near a filter outlet, do stringy white poop, and die within 24-48 hours of showing these symptoms. This cannot normally be...

www.fishforums.net

could I use the flubendazole with the food method? the shrimp will have minimal to no contact with the food

 

[Sgooosh]

 

[Sgooosh]

The fin has been nipped on the big one but other than that it is totally fine

 

[Colin_T]

The big one has excess mucous on its face. I assume the water quality is good and the substrate gets regular gravel cleaning.

It could be old age and the fish are just run down. When that happens they can die suddenly for no real reason.

You can mix medicated food with frozen foods but I don't know how much flubendazole you need to add to how much food.

 

[Ceez]

View attachment 338982View attachment 338983

LOL that fish looks so old he trims nose and ear hair

 

[Sgooosh]

The big one has excess mucous on its face. I assume the water quality is good and the substrate gets regular gravel cleaning.

It could be old age and the fish are just run down. When that happens they can die suddenly for no real reason.

You can mix medicated food with frozen foods but I don't know how much flubendazole you need to add to how much food.

Thank you, I think he only has mucous because I caught him with a net in order to see it's belly if it is sunken in, and he got a little frantic.
Thanks, This is pretty reassuring, they definitely were surrendered to the pet store when I bought them.