Odd die off

[jllapin]

So I have an 8 gallon Nano, very heavily planted with some driftwood as well. I started the tank off with three Danio Erythromicron that have always been extremity shy, swimming to the opposite end of the tank from where I am at all times. I've read this is normal behavior and is not really related to my question but trying to be as detailed as possible. My goal all along was to have Celestial Pearl Danios but started with these because I was having a hard time finding CPDs. After a month or so I located two CPDs and added them, at the same time I added a plant that gave me a nasty snail problem. All 5 fish continued to be very shy. 2 weeks ago I found some more CPDs so I picked up 3 more hoping the numbers would get them out of their shyness, along with those I picked up 6 cherry shrimp and an assassin snail. Last weekend, over the span of a couple days all of the CPDs died but all the Danio Erythromicron were just fine, the shrimp and the snails were unaffected too. I did a water test and ammonia, nitrates, and nitrites all came back zero. I took the water to the aquarium and they tested it as being fine too. The dead fish had no signs of damage that I could see. The temperature of the tank was fine as well. Any ideas on why 5 of one species of fish would die suddenly while 3 of another (very closely related) would be just fine?

 

[absolutangel04]

Hmmm... that is a bit odd. My first guess would be that after 1st fish died, there could have been a small temporary spike in ammonia that your older fish were better suited to deal with since they were more established. Getting sensitive fish acclimated and established is certainly a key part of their ongoing health. My next guess is similar, something may have come in on the new fish and they were not yet established in your tank, and still may have been stressed form travel and relocation so they couldn't deal with it.
I admit, those are a bit of a long shot, but I am not sure what else to tell you.

 

[TheCoolFish]

Yah this happen to me the past week.
I had 1 pleco, 3 Cory's, and 2 cichlid pass. ?

 

[brennae]

I had same prob with cpd. I mail ordered and they died one by one even though I drip acclimated etc. I'm not new at that so I'm not sure what the problem was. delicate little buggers

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[Delapool]

Did you check ph at the same time?