Mystery cory death :(

One of my green laser corys has died. I noticed a couple of days ago that she was pale and lethargic, then today I found her upside down on the gravel, dead. This is her the night before last:

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As you can see, she is almost white and a bit droopy looking. No other symptoms. Do you think she looks a bit thin too? Here is a picture of the other one, for comparison (not a great pic but you can see the colour difference):

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Does anyone have any idea what could have been wrong? They're such tough little fish usually. All perameters are normal, no fish have been added for around three months, and no other fish are showing any signs of illness.

Kally i had the same problem with 2 of my orange lasers they went exactly the same colour, thin and died...i didnt understand why they died either as the others i got are fine.

It confused me at first as it looked like an albino cory rather than what it should have been.
Hope you find out why your cory died,

How big is the tank?
How many are there?
Whats the water quality?
Corys are normally fairly hardy. It might have been internal bacteria/parasites

just lost one of my cories as well, everyone else is ok. I had had it about 3 years..

kizno1 wrote:How big is the tank?
How many are there?
Whats the water quality?
Corys are normally fairly hardy. It might have been internal bacteria/parasites

60 litre divided into four sections via vented clear perspex dividers.
eight corys total, two in each section, plus two male bettas, one assassin snail.
zero everything, pH 6.4, soft water.
No plants or livestock added for months.

My boyfriend and I have been keeping corys for years and never had anything like this occur. No other fish are ill. Nat's corys who died were from the same batch from the same shop.

The 2 remaining are fine and have been since the 2 died in October

KalandraJane wrote:

kizno1 wrote:How big is the tank?
How many are there?
Whats the water quality?
Corys are normally fairly hardy. It might have been internal bacteria/parasites

60 litre divided into four sections via vented clear perspex dividers.
eight corys total, two in each section, plus two male bettas, one assassin snail.
zero everything, pH 6.4, soft water.
No plants or livestock added for months.

My boyfriend and I have been keeping corys for years and never had anything like this occur. No other fish are ill. Nat's corys who died were from the same batch from the same shop.

IMO with the females getting up to 3" long the sections are a little small and they really do need to be in groups, Its safety in numbers and often when not there feel very insecure and often have unexpected deaths.

kizno1 wrote:

KalandraJane wrote:

kizno1 wrote:How big is the tank?
How many are there?
Whats the water quality?
Corys are normally fairly hardy. It might have been internal bacteria/parasites

60 litre divided into four sections via vented clear perspex dividers.
eight corys total, two in each section, plus two male bettas, one assassin snail.
zero everything, pH 6.4, soft water.
No plants or livestock added for months.

My boyfriend and I have been keeping corys for years and never had anything like this occur. No other fish are ill. Nat's corys who died were from the same batch from the same shop.

IMO with the females getting up to 3" long the sections are a little small and they really do need to be in groups, Its safety in numbers and often when not there feel very insecure and often have unexpected deaths.

Fish live in large groups in the wild due to the danger of predation. Sticking with others is a form of self protection because it makes them statistically less likely to be picked off, not because they like each other's company. Fish bred in captivity for generations and generations, kept in an unnatural tank environment, constantly exposed to humans and never exposed to any form of predator are unaware of any danger and perfectly fine in smaller groups. They can see each other through the dividers so were effectively living in a group of eight anyway.

Judging by the fact that I have never seen this type of death despite having kept fish for my entire life, and that Natalie had the same type of deaths in fish bought from the same delivery, in the same tank, ie. their siblings, I'm leaning towards it being some form of congenital defect or underlying infection.

I was thinking the same Kally as they are from the same batch as mine who out of 4, 2 of mine have died.

Also mine dont hang out together only my Julii's do stick together as i now have 6 in my 100 litre, my other corys stay in pairs for some reason

[quote="KalandraJane"][quote="kizno1"][quote="KalandraJane"]

kizno1 wrote:How big is the tank?
Fish live in large groups in the wild due to the danger of predation. Sticking with others is a form of self protection because it makes them statistically less likely to be picked off, not because they like each other's company. Fish bred in captivity for generations and generations, kept in an unnatural tank environment, constantly exposed to humans and never exposed to any form of predator are unaware of any danger and perfectly fine in smaller groups. They can see each other through the dividers so were effectively living in a group of eight anyway.

Exactly they live that way in the wild so they feel more secure and protected when in small groups/pairs they often feel unprotected so they arnt normally as active as they should be and often when you hear of corys dying unexpected deaths there on there own or in small groups, Im not saying thats ther reason why but it does seem like that from a few posts ive read. Seeing each other through a divider doesnt really make much diffence because they still cant shoal or interact in a normally. Not being funny but a 15L tank is edging it for a betta let alone 2 3" very active Shoaling fish. The tanks unsuitable for every type of cory apart from Pygmys.

[quote="kizno1"][quote="KalandraJane"][quote="kizno1"]

KalandraJane wrote:

kizno1 wrote:How big is the tank?
Fish live in large groups in the wild due to the danger of predation. Sticking with others is a form of self protection because it makes them statistically less likely to be picked off, not because they like each other's company. Fish bred in captivity for generations and generations, kept in an unnatural tank environment, constantly exposed to humans and never exposed to any form of predator are unaware of any danger and perfectly fine in smaller groups. They can see each other through the dividers so were effectively living in a group of eight anyway.

Exactly they live that way in the wild so they feel more secure and protected when in small groups/pairs they often feel unprotected so they arnt normally as active as they should be and often when you hear of corys dying unexpected deaths there on there own or in small groups, Im not saying thats ther reason why but it does seem like that from a few posts ive read. Seeing each other through a divider doesnt really make much diffence because they still cant shoal or interact in a normally. Not being funny but a 15L tank is edging it for a betta let alone 2 3" very active Shoaling fish. The tanks unsuitable for every type of cory apart from Pygmys.

I think you'll find the majority of Betta keepers on here who use divided tanks have similar or smaller sized compartments for their bettas and often keep them with corys or similar.

The tank holds 60litres after decor, and the water flow and chemistry all works as one large tank, not four small ones. The reason small tanks are less suitable is because of the propensity toward water quality fluctuations, this is not true of a large tank with dividers. As a system on the whole it is not overstocked, and my corys are all juveniles under 1.5", they take years to reach anywhere near 3".

You should also know that pygmy corys are a lot more active than other corydoras species and actually require more swimming room, despite their small size. No cory is going to be as active in a tank as they are in a river. And you are being funny, because you keep insisting that the death was because of my tank despite clear evidence that there have been identical mystery deaths in Nat's corys from the same batch, who were kept in a larger number and not in a divided tank. I don't appreciate being condescended to by you. Not all of us have the priviledge of having multiple enormous tanks.

On the subject of fish welfare, don't you go fishing? I'm not about to take any tips on how to care for an animal by someone who impales them, partially asphyxiates and traumatises them for their own amusement.

KalandraJane wrote:

I think you'll find the majority of Betta keepers on here who use divided tanks have similar or smaller sized compartments for their bettas and often keep them with corys or similar.

Just because people do it doesnt mean its right. Lots of people keep oscars in a 10G does that mean its fine to do?

KalandraJane wrote:
The tank holds 60litres after decor, and the water flow and chemistry all works as one large tank, not four small ones. The reason small tanks are less suitable is because of the propensity toward water quality fluctuations, this is not true of a large tank with dividers. As a system on the whole it is not overstocked, and my corys are all juveniles under 1.5", they take years to reach anywhere near 3".

Im not saying your tank doesnt have perfect filtration and water chemistry what im saying is that a 15l compartment is no where near big enough for a very active shoaling fish that need to be in groups and get 3" long. From that size they should get there in under a year they do grow fairly quick.

KalandraJane wrote:
You should also know that pygmy corys are a lot more active than other corydoras species and actually require more swimming room, despite their small size. No cory is going to be as active in a tank as they are in a river. And you are being funny, because you keep insisting that the death was because of my tank despite clear evidence that there have been identical mystery deaths in Nat's corys from the same batch, who were kept in a larger number and not in a divided tank. I don't appreciate being condescended to by you. Not all of us have the priviledge of having multiple enormous tanks.

I do know that Pygmy corys are one of the more active corys but the thing is a less active 3" cory will still need more room than a more active 1" cory.
Im not saying thats why they died im just saying the way there being kept wont be doing them any good at all. I never said every one can have "multiple enormous tanks" what im saying is if you dont you should keep fish that are suitable for it, Again thats like saying we cant all have enormous tanks so its fin to keep a oscar in a 10G.

KalandraJane wrote:

On the subject of fish welfare, don't you go fishing? I'm not about to take any tips on how to care for an animal by someone who impales them, partially asphyxiates and traumatises them for their own amusement.

Yeah i do i go quite alot but i dont really see what that has to do with it there to completely different situations. Just because i go fishing doesnt mean i dont look after fish well in an aquarium. Out of intrest do you eat fish? Is that not just as bad?

kizno1 wrote:

KalandraJane wrote:

I think you'll find the majority of Betta keepers on here who use divided tanks have similar or smaller sized compartments for their bettas and often keep them with corys or similar.

Just because people do it doesnt mean its right. Lots of people keep oscars in a 10G does that mean its fine to do?

KalandraJane wrote:
The tank holds 60litres after decor, and the water flow and chemistry all works as one large tank, not four small ones. The reason small tanks are less suitable is because of the propensity toward water quality fluctuations, this is not true of a large tank with dividers. As a system on the whole it is not overstocked, and my corys are all juveniles under 1.5", they take years to reach anywhere near 3".

Im not saying your tank doesnt have perfect filtration and water chemistry what im saying is that a 15l compartment is no where near big enough for a very active shoaling fish that need to be in groups and get 3" long. From that size they should get there in under a year they do grow fairly quick.

KalandraJane wrote:
You should also know that pygmy corys are a lot more active than other corydoras species and actually require more swimming room, despite their small size. No cory is going to be as active in a tank as they are in a river. And you are being funny, because you keep insisting that the death was because of my tank despite clear evidence that there have been identical mystery deaths in Nat's corys from the same batch, who were kept in a larger number and not in a divided tank. I don't appreciate being condescended to by you. Not all of us have the priviledge of having multiple enormous tanks.

I do know that Pygmy corys are one of the more active corys but the thing is a less active 3" cory will still need more room than a more active 1" cory.
Im not saying thats why they died im just saying the way there being kept wont be doing them any good at all. I never said every one can have "multiple enormous tanks" what im saying is if you dont you should keep fish that are suitable for it, Again thats like saying we cant all have enormous tanks so its fin to keep a oscar in a 10G.

KalandraJane wrote:

On the subject of fish welfare, don't you go fishing? I'm not about to take any tips on how to care for an animal by someone who impales them, partially asphyxiates and traumatises them for their own amusement.

Yeah i do i go quite alot but i dont really see what that has to do with it there to completely different situations. Just because i go fishing doesnt mean i dont look after fish well in an aquarium. Out of intrest do you eat fish? Is that not just as bad?

- If it's a baby oscar, fine - upgrade your tank as it grows and obviously they need a huge space as they become full grown. My corys are juveniles and are perfectly happy and active in their current space for now. We have been keeping corys for years, and the largest we have ever had is a female bronze which reached around 2.5" after three years, which was living in a group of four in a very understocked 120 litre tank. The rest of the group never grew over 2", nor have the group of albino corys I have in my community tank. I have seen Sterbai corys larger but not any of the varieties I keep. As far as I am concerned they are a suitable fish, I have been keeping tropical fish and had my own tanks for over twenty years and this is the first time I have ever encountered this type of death or even had a problem with a cory.

- No, I don't eat fish, I am a vegan. I don't eat any animal products including dairy/eggs/fish/meat/honey etc. So yes, I do think it is just as bad, personally. But I think it's totally hypocritical to bang on about the welfare of one type of fish and berate me about my tanks whilst going around inflicting stress and damage to another type of fish, they're all equally as sentient and deserving of life.

Fair enough, IMO its not small enough but i know you know what your doing and at the end of the day there your fish and its up to your judgement.


Fair enough then, i want meaning to berate you in any way just saying IMO i think long term they will get to big and need to be in groups but im not going to get into a argument over it.
I see what you mean but IMO there 2 different thinks just because i go fishing doesnt mean i dont care about fish in an aquarium. I always use barbless hooks and try to stress the fish as little as possible.