Marble hatchet deaths

[jenilew]

Hello...advice needed!!

I have a freshwater planted community tank, it has been set up for approx 18 months. Some of the first fish I bought were six marble hatchets, which have been a delight to own and 100% healthy since going into the tank. Within the past three days I have lost four of them. There are no obvious reasons for death looking at the dead fish and the remaining hatchets look perfectly happy and healthy...yet they keep dying!

Ammonia, Nitrate, Nitrite and ph are all fine.

Any ideas as to what it could be and why only the hatchets are being affected?

 

[pobdave]

Did these deaths occurr shortly after a water change?

Hatchets are very sensitive to water changes and conditioners must always be used.Im thinking maybe your local water params may have fluctuated or did you change de-chloro product?

 

[jenilew]

I change water weekly/fortnightly dependent on conditions and the first one died the day after the last water change. Nothing has changed since the last water changes though...same water, same temp and same conditioner.

I have just watched another one die since I came back from work. There were only the two left and one looked slightly more distanced from the other fish than normal, but swimming about quite happily against the flow. It swam around to the front of the tank and promptly lay on it's side. That was it...completely dead...not even a flinch! It is now 4-5 days from the last water change.

The remaining hatchet (bless it!!) is still swimming around happily and has eaten with the others.

I am wondering whether it is age (I have had them 18 months and not sure how old they were when I got them) or whether they have been harrassed...I have a few of male danios which are particularly 'excited' at the moment and have no where to vent it as the female took a leap of faith out of the tank without me noticing a few months ago. Subsequently they are racing round the tank like F1 drivers unlike the hatchets who preferred a slower pace of life!