My Cory died…what might have caused it?

DomesticGoddess

First off, I inherited a tank of fish from my son when he moved a year ago, and am basically learning as I go! This is the first fish we have had die.

I found one of the Corys died last night (there were 2). I inspected him and noticed some lesions one one side where the pectoral fin was. I included pictures, one of each side for comparison. This fish has always been thinner, less active and more shy than the other. I assumed that was just his personality, but I wonder now if he was maybe sickly.

The other Cory and all other fish in the tank appear healthy and active. I feel like this is likely isolated to this one fish, but what should I do or look out for to make sure the other fish are good?
 

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Flyfisha

Hi DomesticGoddess
Welcome to fishlore

An unfortunate way to join .
Could you please fill out the emergency template?

And tell us a much about the tank as possible.

Its hard to see much in the picture but do you recall it the corydoras had barbells as big as the others? Does the other corydoras have barbells or are the stumps?

Do you have a water test kit?
If not shops will often test water for free , but ask to have the results written down.
 

DomesticGoddess

Hi DomesticGoddess
Welcome to fishlore

An unfortunate way to join .
Could you please fill out the emergency template?

And tell us a much about the tank as possible.

Its hard to see much in the picture but do you recall it the corydoras had barbells as big as the others? Does the other corydoras have barbells or are the stumps?

Do you have a water test kit?
If not shops will often test water for free , but ask to have the results written down.
Sorry for the delay, here’s the information. As for the barbells (back in April), I looked back and found a video with both corys, and this one had stumps. The other one had (and still has) long, pointed barbells.

Tank

What is the water volume of the tank? 35 gallon

How long has the tank been running? 3 years (?)

Does it have a filter? Yes, regular and UV

Does it have a heater? Yes

What is the water temperature? 78

What is the entire stocking of this tank? (Please list all fish and inverts.) 2 dwarf gourami, 1 gold panda Molly, 1 black molly, 1 golden algae eater, 2 Corydoras (well, now 1)

Maintenance

How often do you change the water? Weekly

How much of the water do you change? 25%

What do you use to treat your water? API QuickStart and API StressCoat

Do you vacuum the substrate or just the water? Substrate

*Parameters - Very Important

Did you cycle your tank before adding fish? My son set the tank up, I’m not certain

What do you use to test the water? I just got a test kit…Top Fin

What are your parameters? We need to know the exact numbers, not just “fine” or “safe”.

Ammonia: 0.5-1 ppm

Nitrite: 0.25

Nitrate: 5 ppm

pH: 5.5-6

Feeding

How often do you feed your fish? Twice daily

How much do you feed your fish? I sprinkle some in and it’s usually gone in 5 minutes (either sank or ate)

What brand of food do you feed your fish? Hikari

Do you feed frozen? No

Do you feed freeze-dried foods? No

Illness & Symptoms

How long have you had this fish? 3 years (one of the originals on the tank)

How long ago did you first notice these symptoms? Never noticed any specific symptoms in the time I have had the fish.

In a few words, can you explain the symptoms?

Have you started any treatment for the illness?

Was your fish physically ill or injured upon purchase?

How has its behavior and appearance changed, if at all?

Explain your emergency situation in detail.

(Please give a clear explanation of what is going on, include details from the beginning of the illness leading up to now)
When I came down and turned on the light for the day, I noticed one of the Corys had died. I hadn’t noticed any specific changes, though he’s always looked thinner and been less active and shyer than the other Cory in the tank. Upon examination, I noticed a lesion and missing pectoral fin on one side of the fish.
 

Flyfisha

Ok . Well let’s start by saying all fish species will start to eat any dead tank mate in no time at all. This could explain the damage to the body of the dead fish.

However you have a couple of aggressive species in the 30 gallon.

Dwarf gourami
can be very territorial. I have seen an individual be a total nuisance after dark by watching with a torch. Most dwarf gourami sold are males. Having two in that size of tank is an issue .A stress factor.

The golden algae eater
( also called a Chinese algae eater) has an extremely bad reputation as they grow old . Research the behaviour of these guys and you will wonder why shops sell them. As they mature they case fish of a similar shape which is a stress factor. They can also learn to suck the slime coat of a living fish as it rests.

Corydoras
A species that some people say should be kept in groups of 6 or more. Other people have kept one on its own as that was the practice years ago. In the wild they swim in schools of thousands. In an aquarium you see different behaviour with a group.

The lose of barbells . This could be happening from a bacterial infection. It also happens when they are kept on anything but sand or smooth peddles.

I don’t have a definite answer.
Its possible this corydoras was weaker or submissive to a stronger male. Having lost the barbells food becomes harder to find. If it was a bacterial infection that could have been a contributing factor? No doubt the tank mates were a stress factor?

Having said that 3 years is not a bad time for your families first fish. Yes they can sometimes live longer but in the wild they may not. Like many Amazon river species they can breed in their first year of life for a reason.

Cycling the tank.
At 3 years old the tank should have had an established nitrogen cycle ( good numbers of good bacteria ) . It’s possible when you took over the upkeep you did not fully understand the nitrogen cycle? It’s possible more research on your part to learn more about the good bacteria could be done but it seems unlikely the cycle or lack of cycle had anything to do with this loss? The results of the water test seem to suggest some nitrites ( 0.25) that may require a second test because they will always be zero in a cycled tank. Check your tap water by testing it for ammonia nitrites and nitrates.

Feeding.
We all feed to much.
Feed once a day 6 days a week. This could explain pert of the reason for less than zero ammonia zero nitrites ? Almost all tanks have some nitrates.

Sorry I don’t have all the answers but I hope some of my reply has helped a little. It’s never easy losing fish.:(
 

DomesticGoddess

Ok . Well let’s start by saying all fish species will start to eat any dead tank mate in no time at all. This could explain the damage to the body of the dead fish.

However you have a couple of aggressive species in the 30 gallon.

Dwarf gourami
can be very territorial. I have seen an individual be a total nuisance after dark by watching with a torch. Most dwarf gourami sold are males. Having two in that size of tank is an issue .A stress factor.

The golden algae eater
( also called a Chinese algae eater) has an extremely bad reputation as they grow old . Research the behaviour of these guys and you will wonder why shops sell them. As they mature they case fish of a similar shape which is a stress factor. They can also learn to suck the slime coat of a living fish as it rests.

Corydoras
A species that some people say should be kept in groups of 6 or more. Other people have kept one on its own as that was the practice years ago. In the wild they swim in schools of thousands. In an aquarium you see different behaviour with a group.

The lose of barbells . This could be happening from a bacterial infection. It also happens when they are kept on anything but sand or smooth peddles.

I don’t have a definite answer.
Its possible this corydoras was weaker or submissive to a stronger male. Having lost the barbells food becomes harder to find. If it was a bacterial infection that could have been a contributing factor? No doubt the tank mates were a stress factor?

Having said that 3 years is not a bad time for your families first fish. Yes they can sometimes live longer but in the wild they may not. Like many Amazon river species they can breed in their first year of life for a reason.

Cycling the tank.
At 3 years old the tank should have had an established nitrogen cycle ( good numbers of good bacteria ) . It’s possible when you took over the upkeep you did not fully understand the nitrogen cycle? It’s possible more research on your part to learn more about the good bacteria could be done but it seems unlikely the cycle or lack of cycle had anything to do with this loss? The results of the water test seem to suggest some nitrites ( 0.25) that may require a second test because they will always be zero in a cycled tank. Check your tap water by testing it for ammonia nitrites and nitrates.

Feeding.
We all feed to much.
Feed once a day 6 days a week. This could explain pert of the reason for less than zero ammonia zero nitrites ? Almost all tanks have some nitrates.

Sorry I don’t have all the answers but I hope some of my reply has helped a little. It’s never easy losing fish.:(
I definitely plan research more on the nitrogen cycle as I am interested in setting up my own tank in the nearish future.
The gouramis and corys have been in the tank from the start and I’ve never observed them pay much attention to each other, but I’ve also never observed them at night. We did find out the hard way that they don’t like guppies, but the mollies are fine with them.
Would you recommend rehoming the algae eater, or maybe eventually creating a more suitable community?
Also, should I eventually consider getting more corys? I read that they like to be in large groups, and I’m worried this one will get lonely.
Thank you for your time. It’s hard to have all the answers!
 

Flyfisha

I have never kept a single corydoras on its own but years ago that was how they were kept I am told.

The Chinese algae eater grows big . As it matures it may be more trouble than it’s worth?

The gourami might be ok ?

My suggestion is all of the little things added up to just to much for the smaller weaker corydoras with the injuries to its barbells.


In the future yes corydoras are a suitable species to have in any tank that provides what they need.
 

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