Unexplained Corydora Deaths

emfish

Member
HI Guys,

Recently I have been purchasing Venezuelan corydoras from my lfs however they kept dying when I introduced them into my established tank. So instead I put them into my QT, I had 7 to begin with and am now only left with 2. These ones have been surviving for a while now.

Obviously coz the fish keep dying the lfs owe me fish. So I went in there and they replaced 2 black Cory's. After the second day one of the black ones was dead so I went to the lfs and bought 3 bronze Cory's, and 1 peppered, the next day one bronze was dead and the other was missing... I looked EVERYWHERE.

So then again I went back to the lfs and they gave me
3 black Venezuelan Cory's
2 bronze
2 albino
2 sterbais

That was 2 days ago. Was fine yesterday and the day before. Woke up this morning and an albino and a bronze cory are dead...

Like WHAT IS GOING ON!!!

They are in an established 15 gallon QT
Tested with an API master kit
PH- 8
Ammonia- 0
Nitrite- 0
Nitrate- 30/40

I keep up with water changes. The only thing I can think is that it has been extremely hot in the UK recently. Topping 35- so maybe the temperature change is killing them. I maintain the temperature so I really don't know....

Someone please advise...

I am at a total loss. The smallest sterbaI Cory's are fine yet the bigger more established bronze and albino ones aren't

Emily.
 

DoubleDutch

Member
How is the waterflow Emily ?
Just got a message from a friend that got aeneus-fry from me. She had several dieing lately.

What do you feed (though that wouldn't cause dieing simultaniously).
 
  • Thread Starter

emfish

Member
I have a fluval u3 in there so double the filtration and the head on that produces a lot of flow and breaks the water tension. I also have a bubbler in there. I feed them algae wafers or small corydora sinking pellets
 

DoubleDutch

Member
emfish said:
I have a fluval u3 in there so double the filtration and the head on that produces a lot of flow and breaks the water tension. I also have a bubbler in there. I feed them algae wafers or small corydora sinking pellets
Swap the algaewafers Emily (Corys are on the carnivorious side of te spectrum and don't get nutrition from algaewafers).
As said I doubt it is the cause of death for the new ones.

Did you asked if the LFS itself had dead fish in these batches?
 

irishboy02

Member
Have you dosed with any type of stress coat or relief? Maybe over stressed from the transport home/ capture from the LFS tank. That exact thing happened to me with one of mine. Huge fight to get him out of the tank at the store, never got his color back and about 4 days later he was done
 

Keith83

Member
How are you acclimating them? What are the parameters of the lfs water. What is the temp in your tank? Another possibility is that it looks like you're doing too many at a time. I'd do 2 at a time, max. Corys when under stress actually release a poison as a defense mechanism. In a small bag during transport if a few of them are releasing it, it could wind up being lethal.
 

DoubleDutch

Member
Keith83 said:
How are you acclimating them? What are the parameters of the lfs water. What is the temp in your tank? Another possibility is that it looks like you're doing too many at a time. I'd do 2 at a time, max. Corys when under stress actually release a poison as a defense mechanism. In a small bag during transport if a few of them are releasing it, it could wind up being lethal.
In that case they'd arrive dead and not die after being put in the tank.
 

Keith83

Member
DoubleDutch said:
In that case they'd arrive dead and not die after being put in the tank.
Yeah, in a few minutes in the bag. I've also read that the poison can be released as they are being chased around while netting them. In that case the poison may be diluted enough just to make them sick. Its a head scratcher on why all the Corys are dying on emfish. The parameters seem okay. Could be stress, acclimating process, temp, shock or even already sick fish. Curious that they are all Cory Cats.
 
  • Thread Starter

emfish

Member
DoubleDutch some of their batches have died but they were the sterbais and I still have both of them in my tank... I'm just at a loss...

irishboy02 yes, I dose with stress coat

Keith83 thank you. But when I added 2 at a time or 3 at a time the same thing happened.... I'm not sure what it is
 

Discus-Tang

Member
Have you EVER dosed medication in the tank? Cories are scaleless and therefore quite sensiive to such things.
 
  • Thread Starter

emfish

Member
Discus-Tang No I've never had medication in there at all
 

DoubleDutch

Member
could you please place a tankpic and one of the remaining Cories.

Is the LFS nearby (same waterparameters)?
 
  • Thread Starter

emfish

Member
Lfs has lower nitrate levels. But only by around 20ppm and I do acclimate them over about an hour.

There's some Cory's in the pic
 

DoubleDutch

Member
Mmmm could be the pics but they seem quite thin. Two probable causes :
1. Algaewaferitis as I call it. Not enough nutrition and getting vunerable for infections. Possibly already on a wrong diet in the LFS !
2. Worms.

Feed them different food and watch what happens.
Please give them a (thin) layer of sand.
They benefit of the bacterial growth in it.

Pic of how a C.sterbaI should look.
 
  • Thread Starter

emfish

Member
DoubleDutch what do you recommend I feed them?

I haven't got sand in the tank due to it being a quarantine. Do you think I should put sand in even in a QT?

Emily
 

DoubleDutch

Member
emfish said:
DoubleDutch what do you recommend I feed them?

I haven't got sand in the tank due to it being a quarantine. Do you think I should put sand in even in a QT?

Emily
Shrimppellets a staple food, (froze ) bloodworms, brineshrimp aso.

Ahhh sorry did't realise that. A thin layer of sand can be a good idea though!
 
  • Thread Starter

emfish

Member
DoubleDutch, they are going into a 60 gallon. Just trying to grow them up a bit. I've noticed a few of them stay near the top with their mouth a bit out of the water or find it hard to stay upright. I'm not sure what this could be either....
 

DoubleDutch

Member
Are they gasping or trying to find food maybe ?
 
  • Thread Starter

emfish

Member
You see the albino Cory in the pic. It's like him. But then one of my bronze ones is lying upright in a tree...

I'm not sure if air seems to be coming out of his gills. Maybe ther s too much oxygen in the tank?
 

DoubleDutch

Member
Could you please place a pic of the sinking pellets you're feeding ? What brand is it ?
 
  • Thread Starter

emfish

Member
A mix of these both
Some of the Cory's are now not able to swim and lie on their side. I really don't know her I have done wrong....

Shall I move them over to my 60 gallon? I'm not sure what to do... Think one of the black ones has just died too
 

DoubleDutch

Member
No do not move probably sick fish from the QT to the main tank. Are there other fish in the main tank already and are they okay ?
If so, do a waterchange in the QT with water
from the main tank.

Feed them some of the sinking pellets and leave the algae wafers. Get some shrimppellets as staple food.
emfish said:
Shall I move them over to my 60 gallon? I'm not sure what to do... Think one of the black ones has just died too
 
  • Thread Starter

emfish

Member
I have 3 other tanks and all of the fish are doing fine in them. My Cory's in the 60 gallon are fine too. I just gave the QT Cory's some blood worms. Sadly the black Cory did die. That's 3 today alone... I done a water change yesterday however I will do another one just to be on the safe side. Thank you for your responses

I'm going to leave it an hour to see if they will eat their blood worms and if not then I am going to do the big water change
 

DoubleDutch

Member
Okay, but this time do it with water from the main tank I'd say. That is definitely established. Did the other corys eat ? Edit : I only read the last part now. Clear !
emfish said:
I have 3 other tanks and all of the fish are doing fine in them. My Cory's in the 60 gallon are fine too. I just gave the QT Cory's some blood worms. Sadly the black Cory did die. That's 3 today alone... I done a water change yesterday however I will do another one just to be on the safe side. Thank you for your responses
 
  • Thread Starter

emfish

Member
No, only the albino one ate some. Think a black one ate 1... But there's not really much more I can do...

It's not my fault is it... Do you think it's come from the LFS or it's something I've done?
 

DoubleDutch

Member
One other question Emily. Did you cycle the filter(s)? You spoke about nitrates (that fooled me a bit probably thinking the filters were cycled) but could those be in the tap water already ?
 

Mazeus

Member
I also live in the UK, and I know my local LFS (which is independent, very reputable and regularly win awards) won't stock them because (according to them) the venezualanus in the UK are very weak and die easily.
 

DoubleDutch

Member
They are not C.venezuelanus though.
They are the man-made C.schultzeI "black".
In the UK probably ba quality from the Czech Republic (like Pandas).

But there are other Corys having issues as well (not only the schultzei)
Mazeus said:
I also live in the UK, and I know my local LFS (which is independent, very reputable and regularly win awards) won't stock them because (according to them) the venezualanus in the UK are very weak and die easily.
 

Mazeus

Member
DoubleDutch said:
They are not C.venezuelanus though.
They are the man-made C.schultzeI "black".
In the UK probably ba quality from the Czech Republic (like Pandas).

But there are other Corys having issues as well (not only the schultzei)
My bad, should have read the whole thread. And yes, UK stock comes mostly from the Czech republic.
 
  • Thread Starter

emfish

Member
Yes the tank is fully cycled. Had 5 guppies in it before being QTd and they were in there 6 weeks, and before that it was cycled for 4 weeks so yeah it is cycled.

The nitrates are in the tap water. I do have a nitrate remover filter which I filter the water thought before it goes into the tanks
 

DoubleDutch

Member
emfish said:
Yes the tank is fully cycled. Had 5 guppies in it before being QTd and they were in there 6 weeks, and before that it was cycled for 4 weeks so yeah it is cycled.

The nitrates are in the tap water. I do have a nitrate remover filter which I filter the water thought before it goes into the tanks
Okay then that probably isn't the problem. My guess it is bad stock (wrong diet) from the LFS.
 
  • Thread Starter

emfish

Member
Okay. Thank you so much for your help. So all I can do is feed them up?
 

DoubleDutch

Member
emfish said:
Okay. Thank you so much for your help. So all I can do is feed them up?
I think so. And a waterchange with water from the other tank. The good water to the fish instead of probably sick fish to the water.
 
  • Thread Starter

emfish

Member
Sounds good. Thank you so much
 

Hunterhusker

Member
One thing is you don't want to mix your corydoras species. I did that when I started and I was a no no. I clicked here because mine all died mysteriously. My Julis died after a month or so, no signs of anything. One of my bronzes died so I was left with one. He started to show signs he needed a school so I got him friends. They died and took him with. Now I have a new single pringle. Cory has been doing fine though he isn't stressing from being alone like Elliott did. I seriously went through 20 fish in quarantine trying to get a school for Elliott though. I felt bad and gave up.
 

Chipfu72

Member
DoubleDutch said:
In that case they'd arrive dead and not die after being put in the tank.
Actually, they can die after being placed in the tank after a few days. Several things are factors. The stress of being caught, the stress of being placed in the bag... toxin release... the length of time remained in bad (even more so if acclimated in the bag) and the amount of toxins released (if any at all). Then the stress of sudden light intensity, if the main tank or QT has any.

Not sure how people acclimate their fish.. but is it done before or while in QT? Is your water added to the LFS water?
 

DoubleDutch

Member
Chipfu72 said:
Actually, they can die after being placed in the tank after a few days. Several things are factors. The stress of being caught, the stress of being placed in the bag... toxin release... the length of time remained in bad (even more so if acclimated in the bag) and the amount of toxins released (if any at all). Then the stress of sudden light intensity, if the main tank or QT has any.

Not sure how people acclimate their fish.. but is it done before or while in QT? Is your water added to the LFS water?
That's different info then the article about Selfpoissoning Corys from Ian Fuller is telling in my opinion.

But okay.
 

ssferret

Member
I'm basically a newbie so I hope that I'm not repeating anything or blowing out smoke.

First of all, how much space do you have between your hood and water? Cory Cats need to gulp air every once in the while which I'm sure I'm just preaching to the choir. I have 2 plecos and 4 peppered Corydoras that are doing great in a community tank. What I didn't know, that I'm sure most of you do, is that these fish are happiest in a schools.

I lost 5/6 neon tetras, 2/6 cardinal tetras, and then a female swordtail. The parameters for me was a 7.8 pH, high nitrate, high nitrite, and high ammonia checking the day after a every water change which turned out to be every other day. I was then told that too much water changing is more detrimental than leaving the water alone in a new aquarium set up. The nitrogen cycle needed to be established and stablelized for about 2 weeks. (I don't know if having some plants made that much of a difference.) I would still used an ammonia stabilizer as well as lowering pH to 7.0. After that, a water change every 1 - 2 weeks would be excetable, but I was still skeptical.

I then went on vacation for 10 days (had someone feeding the fish and doing the light cycle) and expected to find dead fish when I got back. I was shocked to see that all of my fish were well and happy. I measured the parameters and pH was 7.6 while the nitrite was 0 and the nitrate and ammonia were in the normal range.

Hope this helps or ignore me and just listen to the experts since I probably didn't say anything you already know.
 
  • Thread Starter

emfish

Member
ssferret thank you so much for your reply. My tank is already cycled so I shouldn't be having the problems with the ammonia or the nitrite, my nitrate levels are so high because of my tap water :/

However for a new fishkeeper you are very well informed. I do a 50% change once a week or 2 25% changes once a week if the nitrate is too high and then I'm putting in 0 nitrate it would be a shock.

Thank you for your response tho and good luck with your fishkeeping! It's an amazing and rewarding hobby
 

ssferret

Member
emfish said:
ssferret thank you so much for your reply. My tank is already cycled so I shouldn't be having the problems with the ammonia or the nitrite, my nitrate levels are so high because of my tap water :/

However for a new fishkeeper you are very well informed. I do a 50% change once a week or 2 25% changes once a week if the nitrate is too high and then I'm putting in 0 nitrate it would be a shock.

Thank you for your response tho and good luck with your fishkeeping! It's an amazing and rewarding hobby
Thank you so much for your compliments. They mean a lot. I try to learn as much as I can but so far I know it's a drop in the bucket. I don't mind. That's why I have you guys.
 

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