Dying Cory's

[Paul]

I have a well established tank (29 gal) with stable parameters pH 6.0, N3 0, N2 0, and Am .25. All the other fish in this tank are doing great. I had a group of Panda Cory's in there for well over a year all's good until abut 6 weeks ago when I found them all dead when I went to feed the tanks. Once I removed all the dead Cory's I treated the tank with General Cure (I followed the treatment procedure). Waited a month all the other fish are still doing great. I even transferred some of the fish into another tank with Cory's in it with no losses. So I get another group of Cory's quarantine them for a couple of weeks then put them in the 29 gallon where all the fish are doing great. I go to feed the tanks the following morning and the Cory's in that tank are all dead. I did notice some bruising on the bodies behind the gills. I don't have this issue in any of my other tanks with basically identical parameters. Any thoughts?

[Cory]

a Ph of 6.0 is very low, at that level it can start burning the skin of some fish. I personally never want my tanks to be below 7.0 ph. I would start by buffering up the water if I was looking to solve this problem in my aquariums. 

[Paul]

 

7 hours ago, Cory said:

a Ph of 6.0 is very low, at that level it can start burning the skin of some fish. I personally never want my tanks to be below 7.0 ph. I would start by buffering up the water if I was looking to solve this problem in my aquariums. 

Cory I know it’s low but all my tanks are running at 6.0 pH (It’s what comes out of the tap) but the only tank where the cory’s, and only the cory’s, are dying is the 29. The low pH of my tap water is why I keep fish (primarily South American) that come from acidic waters.

[Cory]

I can only speak from my experience, when collecting corydoras in the amazon rainforest, I personally never found water that was that low in pH. Most corydoras were at 6.8 to 7 from what we were testing and catching. If your corydoras aren't wild, they are likely bred a much higher pH closer to 7.2 at farms. Everyone's experience will be different of course. 

[Paul]

9 hours ago, Cory said:

I can only speak from my experience, when collecting corydoras in the amazon rainforest, I personally never found water that was that low in pH. Most corydoras were at 6.8 to 7 from what we were testing and catching. If your corydoras aren't wild, they are likely bred a much higher pH closer to 7.2 at farms. Everyone's experience will be different of course. 

Thanks for your input Cory.

[MR aquarium]

i have kept corys for 5 years mainly pygmy corys and they are very hardy but  if the ph gets below 6.4 (the lowest i have ever had ph) they start to act iritated but when i get the ph higher they are fine in my experience. so to me it sounds like ph.