Fish dying in QT

TSM Aquatics


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Jun 14, 2016
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I am totally confused as what is going on with the fish in QT. I started with 6 fish over 2 weeks ago. 3 days into the QT tank, I treated with prazipro for flukes, 2 days later began copper safe treatment. First to die off was a chocolate tang at day 5, then lost a dart fish due to jumping. Day 7 had a orange spot goby disappear and appeared on the floor next few days. Strawberry pseudochromis dead on day 10. Day 11, other dartfish jumped, even having a screen top from day 1. Now the last fish (powder brown) is breathing heavy and listing on the bottom. I did a quick transfer to a small tank with fresh mix and began a 70% WC on the QT tank. I tested some of the water from QT before water change, confirmed no ammonia or nitrates. Got the last tang back into the QT with no improvements. I did treat with prazipro to cover and flukes that might have been missed the first time. Sadly, I don't expect him to make it through the night but I have no idea what is going on. All fish had no spots on them whatsoever, looked fat and healthy but just died, besides the 3 jumpers. Any insight or suggestions appreciated. The only thing that remotely makes sense in my head is cyanide harvesting.


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Nov 4, 2016
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Clarksville, TN
I don't think cyanide poisoning is causing your problems. You don't mention the size of this quarantine tank with all these fish, either. A few things I see here:

1. Fish jumping...why are they jumping? Too many fish in a confined space? Not enough hiding spots for them to feel safe? Quarantining aggressive fish with timid fish (definitely a problem in the fish you listed)? Poor water conditions? Put a screen top on the tank, lower the water level in the quarantine tank so they have to jump a lot higher to get out. You mention a screen top, but you must cover every possible exit hole.

2. No ammonia, but no nitrates? This doesn't make sense...if the tank was cycled, then there would be nitrates. How did you cycle this tank? Are you testing with quality test kits? This many fish require a nicely mature quarantine tank to handle all the byproducts...especially if the tank was smaller sized.

3. Copper and PraziPro treatments at the same time? It can be it recommended to mix treatments? No... Oxygen could also be being depleted rapidly...which would also cause the symptoms you are seeing as well as the jumping. You don't mention the copper concentration? Did you ramp it up slowly or just jump to full therapeutic levels immediately? How are you testing your copper levels? Did you do a water change between PraziPro doses, since you mention doing 2 doses? You should have done at least a 25% water change between doses.

Suggestions now:

1. Big water change to get those meds out of the tank to see if the lethargic fish currently in there can recover. Also, some fish just can't handle copper well.
2. Aerate the water heavily with an airstone and/or pointing a powerhead to the surface for agitation.
3. Monitor the remaining fish for a week or so before starting any additional treatments.
TSM Aquatics

PICK the Most Tested & Least Tested Parameters of your Tank (Pick 2)

  • Calcium (most)

    Votes: 48 6.0%
  • Alkalinity (most)

    Votes: 548 68.7%
  • Magnesium (most)

    Votes: 6 0.8%
  • Phosphate (most)

    Votes: 76 9.5%
  • PH (most)

    Votes: 75 9.4%
  • Nitrate (most)

    Votes: 88 11.0%
  • Nitrite (most)

    Votes: 7 0.9%
  • Ammonia (most)

    Votes: 24 3.0%
  • (least) Calcium

    Votes: 14 1.8%
  • (least) Alkalinity

    Votes: 4 0.5%
  • (least) Magnesium

    Votes: 78 9.8%
  • (least) Phosphate

    Votes: 16 2.0%
  • (least) PH

    Votes: 42 5.3%
  • (least) Nitrate

    Votes: 14 1.8%
  • (least) Nitrite

    Votes: 220 27.6%
  • (least) Ammonia

    Votes: 300 37.6%
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