What The... Why Are They Dying?

[Amunet]

Not sure what is going on but the cories in my 125gal tank are dying.
Every other fish in the tank is acting perfectly normal. Water perims are where they should be.
I just got done doing my weekly water change.

I've found 3 dead cories and the rest are either missing (hiding somewhere in there) or are out and acting strange.
Lethargic and breathing quickly.

Not sure what brought this on. Just all of a sudden yesterday, I found 2 dead cory and noticed one acting weird (the only one out at the time).
Found the other dead one today.

What the heck is going on? What on earth would cause just the cories to get sick and die but not affect any of the other fish?

 

[Tizer]

I assume these are the ones in the 125gal tank? Tiger barbs bully mine a bit, if you dont have enough of them they may stress and die, what temp is the tank? Are you over feeding? Too much left over for the corys to go stupid on?

 

[Harlequins]

Did you disturb any substrate during the w/c ?

 

[Amunet]

I vacuumed up around the edges a bit. There's not really a lot to vacuum up since it's a sandy substrate, it all rests on top.
My tiger barbs don't mess with the cories. Haven't seen any fish mess with them actually.
I may overfeed a little if I'm feeding flake food (which is about twice a week), but I have 2 plecos in the tank that clean up the majority of it.
Tank temp sits around 80F maybe a little less, but I know not more than that.
Everything was perfectly fine before, even just a few days ago, they were all eating and acting normal and then this happened...whatever THIS is. Sigh.

 

[Stoty]

im having a problem too with my cories too and have lost 3. temp is 80. read my post. http/www.fishforums.net/index.php?/topic/368353-cory-trouble-please-help/

 

[Harlequins]

80 is far too high for most corys,they start struggling and it will shorten their lifespan,sterbais are the ones that can handle this temp.

When you added the fresh water,do you temp match? - suddenly adding too hot or too cold can shock fish...

 

[maisy12345]

One of my corries died the night after i did a water change with a thorough gravel vac,how do i prevent this happening again,Harlequin if you think it could be the gravel vac?

 

[Amunet]

My water changes aren't the problem since this started before it and I've never had a problem with it before.
Since it is a large tank, I can't temp match, BUT right now, since it's warm out, the temp of the water does not shift that much. Like I said, never had a problem before, not even when it was freezing outside and the water I had to use was very cold.
Water changes usually made them more active b/c I'd stir up the substrate and they loved to dig around in it.

I've had a few of these cories for years and never had a problem with them before at this temp. They were always very active and healthy.

Sigh..... just found 3 more dead this morning. 2 julii and 1 more panda. Pretty sure one of the juliis was one of my older ones too

If it is the temp of the tank, why would that all of a sudden be causing the problem when it didn't before? Why would it kill ALL of them right this instant?
Not doubting that the temp wasn't ideal for them, but they were doing great in it before. I could understand if they had been showing any signs of being sick from the start, or not thriving, but these were very happy fat little fish

I just don't get it. If it was a water problem, I know a few of the other fish in the tank would've been showing signs of sickness WAY before the cories from past experiences when I've had problems.

 

[maisy12345]

Love to know what`s causing your cories to die ,hope you find out/

 

[Amunet]

I doubt I will find out the problem
I managed to catch the last remaining panda cory and put it in to my 29gal tank to see if it would improve at all. So far, nothing.

There are 4 cories left in the large tank. 3 skunks that are years old, and a lone julii. All of them are showing signs of stress. Probably doesn't help that I tried catching them earlier, so that's my fault. They've all been hiding from me for the most part.

Hope I won't wake up to find that they have died as well

 

[Harlequins]

Its strange its only affecting the corys...

I hope the rest pull through

 

[Amunet]

Have 5 left out of all of them. My 3 skunks are left, but not sure they're eating. 1 julii that looks like it is foraging and acting normal, and 1 panda left that I moved back in to the large tank so not sure if it's acting normal again or not.

I'm watching my plecos right now since they're bottom feeders as well just to see if they start acting strange.
I still don't know what could've caused all of this.
Poor cories

 

[Amunet]

Alrighty, so update.
Just found my large pleco dead and the other smaller one isn't looking too great and will probably soon follow.
Dangit.

The rest of the fish still look perfectly healthy and are acting totally normal.
The pleco must've been just as sick when the cories started to die, I just didn't notice since I thought it was just acting like it usually does.

Not sure what went wrong here. Why would all of the other fish be ok, but only the bottom feeders be affected by whatever happened?

I've kept an eye on water perims and everything has been totally normal. No weird fluctuations, no sudden spike in ammonia, nitrites, etc.

I cleaned the filter yesterday (yes, I did it properly), and did a water change, still totally normal water readings now.

Remaining fish (except for the other plec and the remaining cory) are acting normal and healthy.
The sick fish show no outer appearance of being sick other than not eating and not moving around much. No weird funky fungus spots, no sores, nothing.

 

[Tizer]

what were your ammonia and nitrite readings? sounds like something to do with the water to be honest.

 

[Amunet]

Ammonia is 0, nitrites 0, nitrates 20 or so. pH has been sitting around 7.
The water is perfect, moreso now b/c of the water change.