# Why my Corys



## Nave (May 28, 2013)

I got up this morning to find that 4/5 of my Cory cats died last night I don't understand why it was just the Cory cats. All of my other fish look fine show no sign of stress and have all there color. My water is fine 0 ammonia 0 nitrite and between 10 and 20 nitrate. My tank is a little on the warmer end as we have been having a heat spell here its about 82f does any one have any idea as to why just these fish bellied up all at once? And why all my other fish are ok. I'm still going to treat my tank just in case it was a bacterial infection.


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## coralbandit (Jul 29, 2012)

What were you feeding the cories and do you KNOW they were getting to eat it?Who else is with them and what size tank?


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## Nave (May 28, 2013)

I was feeding them API bottom feeder shrimp pellets. They were in a community tank with a variety of tetras bristlenose pleco a gourami and a couple rams. I never saw any aggression and watched them eat every day.


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## coralbandit (Jul 29, 2012)

They are for the most part vegetarians and shrimp pellets are high protien(for carnivores).Algae wafers would be a better choice and the pleco WILL out compete them every day(that ends with a "Y").
What kind of gourami(they are usaully much tougher than people think)?


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## Sebastian (Dec 27, 2012)

Is the tank 82F? That would be a little hot for most cories, but probably not yet lethal. I know some fellow discus keepers who had problems keeping cories alive at higher temperatures.


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## Nave (May 28, 2013)

I do feed algae wafers as well. I know the pleco can and will out compete for food but I would watch them all eat as their the most entertaining in that tank. The gourami is a dwarf It's less the 3" I think it's about full grown. Im thinking the water was too warm for them thrive in I just find it very odd that 4 died in one night, and all the rest of the fish in the tank seem to be ok. Would it be wise to continue to treat my tank?


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## Jaybird5 (Apr 27, 2013)

I would not. If you do not know the problem why treat? Meds just really stress the fish.


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## Nave (May 28, 2013)

Even natural stuff like Pima and melafix?


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## coralbandit (Jul 29, 2012)

Prima and melafix are BUNK products IMO! and could be the untimely end of your gourami!
http://www.aquariumforum.com/f5/use-melafix-pimafix-betafix-labyrinth-organ-2363.html


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## susankat (Nov 15, 2008)

Cories do take more protein and really aren't algae eaters, when they pick at algae they are picking off any little critters that grow there, like rotifers and such. Most cories can't stand that warm of a tank for a given length of time so that would depend on what type of cory it was.

Cories also when stressed will secrete a poison and if they were all in close proximity will kill several around them.


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## Nave (May 28, 2013)

I read that thread it was very interesting and I will not continue to med that tank thanks for the link. The shrimp pellets I have are "enhanced with seaweed" and I did see them eating the algae wafers as well. The Corys I lost where two albino one emerald and one panda. I'm really upset this happen as I love these cats fish they are very active and fun to watch.


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## StevenT (Jun 11, 2013)

I was having problems with my corys when I first started keeping them. It turned out to be my substrate. You see I had a rocky substrate and they need a sandy one. Turns out they were having trouble eating even though it looked like they were. I changed it to sand and they thrive now.


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## Nave (May 28, 2013)

I'm just stumped as to why they all died in one night I find that very strange. If it was a feeding issue they would've gone one by one, I would think the same for a temp problem as well.


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## Nave (May 28, 2013)

susankat said:


> Cories do take more protein and really aren't algae eaters, when they pick at algae they are picking off any little critters that grow there, like rotifers and such. Most cories can't stand that warm of a tank for a given length of time so that would depend on what type of cory it was.
> 
> Cories also when stressed will secrete a poison and if they were all in close proximity will kill several around them.


This poison, would it kill other species fish too or just other cories?


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## Goby (Mar 21, 2012)

Nave said:


> I'm just stumped as to why they all died in one night I find that very strange. If it was a feeding issue they would've gone one by one, I would think the same for a temp problem as well.


You're right...death by disease or poor nutrition, including starvation, doesn't work like that. It's generally not sudden. But stress and inadequate nutrition does affect a Corydora's ability to cope with fluctuations in water chemistry...which can result in sudden death. That said, nothing you've shared suggests to me that nutrition was an issue. Yet still, it's something worth considering. And Corys can acclimate to 82 degrees providing the water stays at a steady 82 degrees. 

If your tank is less than a year old, you likely have your answer. Cory's are beyond sensitive to even slight water fluctuations which are, without exception, always present in newer builds. There's no getting around that, no matter how clean your water is or how correct your parameters _seem_ to be. Also, if the air outside of your tank is being allowed to regulate the temp inside your tank, that increases water instability in ways that go far beyond temp...I'm talking gases, ion bonds etc. Cory's are even sensitive to routine partial water changes. I have no idea why pet stores and vendors categorize these fish as "easy" and for "beginners" because they are neither of those things. They are the exact opposite of those things. And I lied...I do know why retailers do it...it's all about the $.

Cory's are super fun...I'm very much drawn to them. But I understand that if I put them in a tank that's less than a year old, they are at high risk for death. The fact that you lost 4 at once suggests a water issue...likely a swing of some sort followed by a correction.

Don't blame yourself. Blame the industry that presents Corydora's as something they're not- "for beginners". Try again when your tank is at least a year old and even then, expect a higher than average mortality rate. As your tank ages, the Cory's will too. My mom has kept the same Cory's for what seems like decades. Some individuals well beyond 10 years, maybe beyond 20.


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## susankat (Nov 15, 2008)

I have 12 species of corys and really the only ones that like that are sterbai, weitzmani and adolphi. Those I keep at 82 to 85. the others do best at temps between 77 to 79. 

I have several cories that are in tanks less than 6 months old that are doing fine. As long as the tank is cycled, temps are right for the particular species. Kept well fed

As for the poison it can kill other fish but not likely as they prefer large groups as possible. Large groups will usually spread out to smaller cliques and and its the smaller groups that get the poison because of the proximity.


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## Nave (May 28, 2013)

Goby said:


> You're right...death by disease or poor nutrition, including starvation, doesn't work like that. It's generally not sudden. But stress and inadequate nutrition does affect a Corydora's ability to cope with fluctuations in water chemistry...which can result in sudden death. That said, nothing you've shared suggests to me that nutrition was an issue. Yet still, it's something worth considering. And Corys can acclimate to 82 degrees providing the water stays at a steady 82 degrees.
> 
> If your tank is less than a year old, you likely have your answer. Cory's are beyond sensitive to even slight water fluctuations which are, without exception, always present in newer builds. There's no getting around that, no matter how clean your water is or how correct your parameters _seem_ to be. Also, if the air outside of your tank is being allowed to regulate the temp inside your tank, that increases water instability in ways that go far beyond temp...I'm talking gases, ion bonds etc. Cory's are even sensitive to routine partial water changes. I have no idea why pet stores and vendors categorize these fish as "easy" and for "beginners" because they are neither of those things. They are the exact opposite of those things. And I lied...I do know why retailers do it...it's all about the $.
> 
> ...


Thanks for the info Goby you are right that my tank is not new i just set it up in march this year. I also happened to do a large water change just the day before this happened and cleaned one of my filters. Most of the cories did typically hang out together and the peppered Cory was the Lone Ranger if you will, that's the one that lived. I will try again in the future cause I really do like these little fish they were some of my favs in the tank.


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## Nave (May 28, 2013)

susankat said:


> I have 12 species of corys and really the only ones that like that are sterbai, weitzmani and adolphi. Those I keep at 82 to 85. the others do best at temps between 77 to 79.
> 
> I have several cories that are in tanks less than 6 months old that are doing fine. As long as the tank is cycled, temps are right for the particular species. Kept well fed
> 
> As for the poison it can kill other fish but not likely as they prefer large groups as possible. Large groups will usually spread out to smaller cliques and and its the smaller groups that get the poison because of the proximity.


This is interesting too Idk the scientific names of my fish but I'm wondering if the pepper Cory is one that does fine with warmer temps and the theirs where from cooler climates. As far as tropical fish go tho 82 degrees is pretty warm IMO but most of these fish will acclimate to this temp. I think between what Goby and Susan have said hits the nail on the head and thank you guys for your input.

Oh and as goby said that pet stores label these fish as beginner fish. I don't think these stores (especially corporations like petsmart and petco) don't label these fish off of there care needed thru water parameters but more of the aggression. If you look all of the community schooling fish are labeled "beginner" and as you get more semi aggressive fish their considered intermediate, then you get to the various cichlids and most all are "advanced". I too find this to be a bogus system as some of the cichlids for instance the convicts and jack dempsey are both fish that are very easy to care so long as aggression in the tank is minimal. If you look at care guides for these fish you really have to intentionally sabotage your tank (don't do that) to kill off these fish. They both can with stand a wide range of ph, hardness, and temp.correct me if I'm wrong about any of this its just what I have read more then experience.


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## Goby (Mar 21, 2012)

Nave said:


> Thanks for the info Goby you are right that my tank is not new i just set it up in march this year. I also happened to do a large water change just the day before this happened and cleaned one of my filters. Most of the cories did typically hang out together and the peppered Cory was the Lone Ranger if you will, that's the one that lived. I will try again in the future cause I really do like these little fish they were some of my favs in the tank.


Peppered Cory's are more hardy than other varieties of corydoras. IMO, they are the hardiest. So, I wouldn't hesitate to put a few more peppereds in your tank...now. Your sole peppered cory will be miserable alone, and cory's prefer to shoal with members of their own genus anyway. In my experience, you'll witness more interesting behaviors amongst a genus group versus a group of conspecifics...not that mixing is wrong and not that conspecifics won't enjoy each others company. I've also found albino cory cats to be more tough than some of the other varieties.

And I agree...what's a FW community tank without a shoal of cory's?


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## Goby (Mar 21, 2012)

corydoras paleatus = peppered cory

Their temp needs are about the same as a panda or albino cory...72-80 and ideally somewhere in the middle. IMO, most cory's can do a steady 82...that's not to say the higher temp didn't contribute to their demise. With regards to the sudden death of 4 corys in water of 82 degrees... I'd look less at the number 82 and more to the freedom the water was given to fluctuate above and below that number. That messes with water chemistry, more so in a young tank.

Check this out...

Corydoras Catfish For Sale: Cory Cats in Many Varieties


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## jrman83 (Jul 9, 2010)

How big was the water change the day before and what was the temp difference between water going in and the water that was in your tank? Big water changes, >45%, can lead to big temp swings. I have affected many fish in this way back when I first started on much more sturdy fish than Cories.


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## Nave (May 28, 2013)

The water change was about 40-50% I use a thermometer to make sure the water I am replacing is the same temp.


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## jrman83 (Jul 9, 2010)

Nave said:


> The water change was about 40-50% I use a thermometer to make sure the water I am replacing is the same temp.


Good practice. My gut feeling says the deaths were related somehow to the water change. There is just too much coincidence for any other explanation in my mind.

I would just mark it up as one of those things. It won't be your last I assure you - if you stay in this hobby.


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## Nave (May 28, 2013)

I think your right the water change was just too much for them to handle. I know it's not going to my last loss I was just blown away, four at once? I was under the assumption you can't change too much water so long as your colonies stay alive, I proved that theory wrong. And I'm not going any where from the hobby I love my tanks, I replaced my tv in my room with one and enjoy it much more then some bogus show. I watch my tank for hours their very entertaining and comforting to watch. IM NOT GOING ANYWHERE!!!!


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## Goby (Mar 21, 2012)

Nave said:


> I think your right the water change was just too much for them to handle. I know it's not going to my last loss I was just blown away, four at once? I was under the assumption you can't change too much water so long as your colonies stay alive, I proved that theory wrong. And I'm not going any where from the hobby I love my tanks, I replaced my tv in my room with one and enjoy it much more then some bogus show. I watch my tank for hours their very entertaining and comforting to watch. IM NOT GOING ANYWHERE!!!!


What a great post...and attitude.


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## jrman83 (Jul 9, 2010)

Nave said:


> I think your right the water change was just too much for them to handle. I know it's not going to my last loss I was just blown away, four at once? I was under the assumption you can't change too much water so long as your colonies stay alive, I proved that theory wrong. And I'm not going any where from the hobby I love my tanks, I replaced my tv in my room with one and enjoy it much more then some bogus show. I watch my tank for hours their very entertaining and comforting to watch. IM NOT GOING ANYWHERE!!!!


Don't shy away from large water changes, although I see where you could. I change 60-75% (large and small tanks) weekly on my tanks and although I have had my fair share of losses over the years they have been related to other things and isolated issues.


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## Jim Albright (Jan 22, 2013)

The only way it was from the water change was if the water temp was too much of a change, didn't use a dechlorinator or you completely sucked out all the good bacteria. I have done big water changes for yrs and haven't lost fish like that. Also, are you adding beneficial bacteria when you change the water...ie api stress zyme?


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## Nave (May 28, 2013)

I use stress coat. This particular tank is a 55 gal I an running an AC 110 and an eheim 2215 on it. Between the two filters I should have plenty of bacteria colonies to support a large water change. I tested the water the morning I found the fish and showed 0 ammonia and nitrites my nitrates where under 20ppm.


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## Jim Albright (Jan 22, 2013)

I only use stress coat when a fish has been netted or I feel the fish are stressed out. I use Prime to take care of my dechlorination and tap water issues. Seems to be working well for me.


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## Nave (May 28, 2013)

Prime is a very good product I use it as well. I try to save my prime when I'm not having a water quality issue as stress coat removes chlorine and calms the fish during a stressful time such as water changes.


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## Goby (Mar 21, 2012)

Jim Albright said:


> The only way it was from the water change was if the water temp was too much of a change, didn't use a dechlorinator or you completely sucked out all the good bacteria. I have done big water changes for yrs and haven't lost fish like that.


A sudden and significant change in water temp is just one of the reasons fish can die or get stressed after a drastic water change. There are a number of chemistry changes in addition to temperature, that can happen after a massive water change...and if those chemical shifts occur too drastically and too quickly, fish can die. Fish can die after large water changes even when the water chemistry has been significantly improved. Their bodies simply aren't able to adjust quickly enough.


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## Nave (May 28, 2013)

My poor cories... Wish I had known. Well we all learn from our mistakes and some of us learn from others mistakes hope this will help someone in the future, it helped me thanks for all the tips and info from all of you to help figure this thing out.


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## Goby (Mar 21, 2012)

Nave said:


> My poor cories... Wish I had known. Well we all learn from our mistakes and some of us learn from others mistakes hope this will help someone in the future, it helped me thanks for all the tips and info from all of you to help figure this thing out.


Well dammit it just sux that that had to happen to you and your cories! I wish I could just go buy you 4 more. If you lived by me, I would...I'm super weird like that. 

Don't be so hard on yourself. I've been doing this for 30+ years and I still make mistakes. Fish keeping is a constant learning process...sometimes I learn things that I already knew but forgot until I killed something again.

I think you're doing awesome and any fish would be lucky to have you. :fish-in-a-bag:


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## Nave (May 28, 2013)

Thanks goby that's very kind of you  I will pick up more pepper cories that way the one that's in there isn't so alone. And thank you again I'm doing what I can to keep my tanks happy and healthy.


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