Hatchet Fish Horror.

[bigcheed]

a month ago i introduced 4 marbled hatchet fish to my community tank. one died a few days later but the others did marvolously well. they seemed to love my tank and would become very excited at feeding time so after three weeks i decided to get some more. last saturday i bought 6 more. in the last week all but one of the new fish have died, but so have my exsisting fish as well. up now ive lost 3 cardinals and 3 endlers. all at random times with no signs of disease. they can be fine in the morning and a few hours later dead. all the other inhabitents seem fine. active colourful and feeding. all my water perameters are good. amm 0 nitrate 0 nitrite 5. ive been keeping fish for a couple of years now and dealt with ich droppsy and most of the usual suspects but this is a real head scratcher. my tank is 125l planted set up and up last sat was my pride and joy. its really upsetting to keep finding dead fish. any help or advice would be most welcome. thanks folks.

 

[attibones]

I hope you mean your nitrate is 5, not nitrite! Nitrite at 5ppm would be very deadly and probably the cause for all your troubles. However, I don't suspect this is the case.

The new fish probably brought in something internal. Are you noticing any odd poos lately?

 

[bigcheed]

sorry yes got that the wrong way around. nope no strange poops.

 

[Byron]

I am no expert in disease, but I have myself had this occur twice, so I will offer my observations.  
 
Given that the tank has been running successfully for so long, it seems little doubt that the latest hatchets introduced a disease, and given the rapidity it has spread and that you are seeing no external signs as you would with ich and such, it is most likely an internal protozoan.  This is very common in commercially-raised fish these days.
 
I would suggest feeding with food medicated with metronidazole.  You can buy this direct in the US, I am not sure about the UK.  I cannot get it in Canada.  But you can also buy the drug metronidazole and mix it with fish food.  Seachem sell it under the same name, Metronidazole; it is a white powder and you mix it with flake food in a zip-lock bag.
 
I learned my lesson after losing almost half the tank of fish, twice, to this.  Though introduced with tetra, it spread most rapidly through my hatchets (marble and silver) and I lost most of them within days.  A microbiologist friend put me on to the metronidazole and after a few days the deaths stopped.  Quarantining all new fish for several weeks is the only way to prevent this or similar diseases.
 
Byron.

 

[Bugdozer]

I don't think metronidazole is sold freely in the UK - it's an antibiotic used in human medicine and if it gets flushed out into the environment in old fish tank water it increases the speed with which resistant bacteria are likely to develop. Hence, we have restrictions on its use.

 

[bigcheed]

thanks all for the advice. to update ive gone for interpet anti internal bacteria. there have been no more fish deaths today. again all the fish seem fine and healthy. i will keep monitoring them closley and hope for the best with the treatment. fingers crossed.