Stumped About Cory Die Offs

[NeonBlueLeon]

 

 
Someone correct me if I'm wrong, but I don't think there is such thing as "too many water changes."  My water changes are always matched in temperature.

yes, you can do too many water changes..
 

So how many water changes is too much?

 

[NeonBlueLeon]

So, I've returned the skunk cories.  My LFS has now stocked corydoras hastatus!  I don't know if I'll get them though since I want to just increase my rummynose school size and leave the tank alone.  The guy working at my LFS said corydoras hastatus spend more time in the water column thank other cory species.  Anyone know if that's true?  Just curious.

 

[Lunar Jetman]

So how many water changes is too much?

I'm not sure that there is an easily identifiable point where it becomes too much but I would say in your case you either change 50% once a week or 2-3 10% changes a week, not both.

Personally I would only ever do a 50% change when I want to remove something from the water so I only change around 25-35% once a week.

Dosing EI for plants might mean you want to do 50% once a week though.

 

[DoubleDutch]

So, I've returned the skunk cories.  My LFS has now stocked corydoras hastatus!  I don't know if I'll get them though since I want to just increase my rummynose school size and leave the tank alone.  The guy working at my LFS said corydoras hastatus spend more time in the water column thank other cory species.  Anyone know if that's true?  Just curious.

True. There is one other Pygmaeus doing the same thing.
OMG I'd like to have some Hastatus over here. Already keeping Pygmaeus, Habrosus, this is the missing dwarf hahahaha.

 

[RCA]

+1 with Double Dutch, I have just got ten Pygmaeus, currently in quarantine. Shame you took the survivors back, they may well have continued to thrive, as per my survivor below.
 
The other thing to consider is pH, I understand these Cory's need a pH of 6.2-7.2.  That said I would also try and find out the source, as to whether they were wild caught or tank bred, as this too can make a difference to how they acclimatize.  I had a similar situation with four Aldolfo Cory's, they were slowly drip acclimatized and yet one by one, each day another had died, with one survivor*.  It was not my usual LFS and when I called to ask if there had been an issue with them, they said no one else had called in - but they have never seemed to have stocked them again!.  I more latterly, against my better judgement bought four new female Bettas from this same store, within 24 hours, three were gone and the other was dead on my arrival back from the LFS - who tested my water and it was spot on!  Needless to say I no longer buy fish from this store.
 
If you can, set up a small quarantine tank.  This can make all the difference in settling in new fish and giving them the opportunity and watching them feed.  You can take some media from your existing filter when needed.
 
In terms of feeding, I use a moist pelleted food now as well as the traditional and I find this sinks fairly quickly so all the fish get some, especially the Cory's.
 
*My one survivor is a female and she has just been laying eggs 

However, at present she lives with Panda Cory's, but this week I pick up four more Adolfo (ordered five) and six Orange Lazer Cory's that I ordered 

 

[NeonBlueLeon]

Thanks for the remarks!   I haven't gotten any of the dwarf cories yet, mostly because they are in a LFS I don't trust.
 
RCA, I know what you're saying about how some LFS sell fish that just tend to die.  I have one that have something like 80% die off rates.  I too do drip acclimation.  Of course, I no longer buy from there either.  Also, Petco fish tend to die a lot as well.
However, the skunk cories I bought came from a LFS that has superb, healthy fish.  Every tank they have has its own water and filter.  The fish I buy from them rarely die.  Therefore, it was all the more alarming when the skunks started dropping.
 
I have a QT, and do exactly what you described with the filter media.  I decided to risk the skunks because my QT was being used at the time (especially since I trusted the LFS they came from so much).  The rest of the fish in that tank are still doing great today.