[peterlista]

I bought a dozen CPDs from a LFS and started quarentining them after drip accimating. This morning (three days later), I noticed three fish with bouyancy issues -- two floated and the other sank, seemingly outside of their control -- which died a few hours later. I now have a fourth fish that has started to slowly float to the top of the tank. The fish look healthy otherwise, with no signs of infection or parasites (though I have started treating for both just in case).

I'd appreciate any thoughts you have as I really hate losing fish like this.

Edit:

7.4 PH
7 dGH
4 dKH
0 ppm Ammonia
0 ppm Nitrite
5 ppm Nitrate

 

[ichthyogeek]

I'll try my hand at this:

Was the fish floating up from its tail or from its mouth? What have you been feeding the fish? What temperature is the tank?

 

[peterlista]

I'll try my hand at this:

Was the fish floating up from its tail or from its mouth? What have you been feeding the fish? What temperature is the tank?

Two head first and one tail first, interestingly. Since I posted this, I've treated with salt and have had no other deaths.

 

[Discusluv]

If the deaths came 3 days after acclimation you can rule out acclimation issues. That would happen within 24 hours.
I doubt its parasites. The only parasite that can kill that quickly once introduced to the aquarium is Ich, and you would see the signs on body of fish if getting to the point of dying. Internal parasites killing en masse over days is also unlikely within given time-frame.
That leaves a common illness of newly acclimated fish that can show no symptoms or signs up to death- Columnaris. Columnaris ( a gram negative bacterial infection) has 4 strains that have differing levels of quickness in killing fish. The most rapid can kill within 24 hours. The least quick developing will kill fish slowely-- one at a time-- over months.
The lifeless swimming is indicative of internal organs shutting down- which caused weakness and lethargy.
Treatment is a combination of nitrofurazone ( Active ingredient in API Furan 2) and kanamycin (Active ingredient in Seachem Kanaplex.)

 

[ichthyogeek]

It's saltwater, but this may also be helpful in diagnosing what happened:

Internal Issues

Internal Issues For simplicity’s sake, there are 6 basic problems a marine fish may experience on the inside: 1. Intestinal worms Symptoms: White stringy feces, pinched stomach, fish has faded coloration, fish eats voraciously but still seems to be losing weight. Treatment of choice...

humble.fish