Cardinal tetras dying

What about the danio though? That's what worries me. :( I *did* do a more thorough gravel vac than normal, but it was days ago, I can't imagine that would make a difference. Now I think my magenta brigg in my other tank is dead. :( But all the 3 week old cory fry are fine. This is so frustrating. :(
 
Oh, i just tested bioth tank- 0 across the board in the 5 gallon (which make sense the tank wasn't really cycled when I added the fry I do lots of WCs) and 0-0-5 in the 29. pH, gH and kH same as above.
 
Could it just be a horrible coincidence with the Danio?
 
The danio death could have been a result of the elevated ammonia level. Some fish are more sensitive than others, even the same strain of fish you'll see stress response variations. Most important thing, keep checking your levels daily or 2X a day for a few days. Make sure that ammonia doesn't rise again and watch the nitrite doesn't come up either. Fingers crossed that the cards didn't bring any illness into your tank.
 
Well false alarm on the snail anyway, lol. Not the first time he's faked me out.

I'm hoping the danio was a coincidence or more susceptible for some reason or another. I'm a little paranoid now, I was examining the danio,s and thought "OMG that one has red patches on it's belly!" And then I realized the it was the danio x glofish cross that is mostly red. :o

Anyway, hopefully the cards were just bad stock, and I'm setting my new 10 gallon up now. I should be able to QT some more cards before I need to move the cory fry in there. I just hate the idea of schooling fish being lonely. :(

I might go for a bigger school anyway, there may just not have been enough of them against the 12 (now 11) danios.
 
I've always heard Cardinals and Neons are die off species- you can expect a number to die from whatever you buy.

The Danio could have died from the amonia- but you really wouldn't expect a Danio to die before the rest of the Cardinals and/or the Cory. Danios are often used for cycling- they're tough little guys.

Still if he were old or weak maybe so.
 
Well everyone's ok this morning, so that's a relief, and the water params are normal. Crossing my fingers that this is over.
 
AquariaCentral.com