[Peacelily]

Two weeks ago I introduced nine white cloud mountain minnows into a recently cycled aquarium. One of them became somewhat lethargic and stopped eating, then died a few days later. The same thing happened to a second fish this past weekend, and as of today a third fish ignored food during feeding time. I can see no physical abnormalities, either when alive or on inspection after death.

Water parameters:
Ammonia - none detected
Nitrite - none detected
Nitrate - about 10 ppm (not certain -- I have a hard time reading the API color chart around 10-20 ppm)
Temperature - 70 F
pH - 7.8
dKH - 2
I don't have a GH test, but I found a study listing the tap water here in Pittsburgh at around 5 dGH (87 ppm)

They all seemed healthy and behaved normally before I moved them to the new aquarium. The move had to be stressful, though. We've just moved into our new house, and they got jostled a lot during the move across town. But if this is related to the move, why is this happening two weeks later?

Any ideas?

 

[Sylverclaws]

How big is the tank? When add that many at once to even large tanks it can cause a rise in acidity that can make them lethargic and then kill them.

You should only add 3-4 fish a week to an established tank, yours being recently cycled it may not have been able to handle it.

If the tank is under 25-30 gallons, it may be staying there and since they like to swim it'll be stressful in smaller areas. Have you dine any water changes since you got them? If not, I suggest you do a normal 25-30% change now. Use Prime to condition the water if you have any, that will detoxify your nitrates if that tiny amount is bothering them. Normally under 20ppm it doesn't, but they were stressed and may not have been able to recover after the acidity rose in the tank.

 

[Peacelily]

You're right, it wasn't good to move so many at once, but I worried about having less than six in either tank -- yet another form of stress. The aquarium is a 40 gallon long (basically, a short version of a 55 gallon). It's a planted aquarium with a sand substrate (light-colored) and LED lights. I initially had some floating plants in there (hornwort and duckweed) plus Java ferns and marimo moss from the old tank, but last weekend I added some anacharis since it still seemed too bright, plus some jungle vals. Do you think the light level might have been a problem?

The pH has dropped about .2 or .3 since I added the white clouds, and that's probably too much for a two week period. I haven't detected any ammonia or nitrite, though I didn't keep a good eye on it last week while we were moving into the house.

I don't have Prime, just the API stuff that removes chlorine/chloramines and promotes slime coat.

What's really strange about all this is that one of the females was spawning on Monday, and at least two of the males mated with her (possibly more, but I missed part of the action). Does it make sense that some of the fish would be feeling well enough to mate, while others would get lethargic and stop eating?

 

[Sylverclaws]

It does. Like with people, animals get hit differently by things.

Ah, it could be a number of things. After effects of the rise in acidity, low immune systems and poor slime coats and problems from previous care allowing some to be hit harder than others.

A lot of times fish wont eat for a few days to a week in a new place, but you said some were ok at first. If not problems with water, I'm assuming some were either ill, or something has stressed them out.

Do you have enough plants and hiding places for them to chill out and start feeling more secure? If not, more places to hide may help.

Make sure none are being chased, nipped or bullied by the others. Sometimes they do. =)

 

[Peacelily]

The hiding places were fairly limited until last weekend. :-( Something to keep in mind in the future. We're thinking of setting up the old (29 gallon) aquarium as a tetra tank, so it's already planted. I initially thought it would be enough, but now I think I should probably add more plants before we bring any fish home.

The white clouds I lost were newer acquisitions (April) and weren't full grown yet. The one who's lethargic now is one of the older ones and wasn't at the bottom of the pecking order, so I'm hoping it will have the stamina to recover.