Angelfish- Water Change Poisoning

Discussion in 'More Freshwater Aquarium Topics' started by LakeMann, May 22, 2019.

  1. LakeMann New Member Member


    I just got back home from college. My parents thought it would be nice to clean my fish tank for me before I arrived. They did a complete 90% water change. Yesterday, two of my freshwater angelfish (scalare) had clamped fins and stayed at the top of the tank (not gasping for air). One of them died this morning, the other is still exhibiting the same symptoms.

    125 Gallon, and water parameters are 0 ammonia, 0 nitrite, 20 nitrate. 78 degrees F.

    However, only specific angelfish from the same breeder are affected. All the other angelfish are fine. Anything I can do to increase the survival chance of the remaining angel? Also is genetic susceptibility to water sensitivity at play here?


  2. nikm128 Fishlore VIP Member

    Do you know if they treated the water? Temp matched?

  3. LakeMann New Member Member

    Yes the temperature match and the water was dechlorinated.
  4. bizaliz3 Fishlore Legend Member

    a 90% water change is pretty large. And if there is a significant PH difference or something like that between the tap water and tank water, it could have caused them some shock....weakening and ultimately killing them?

    OR if the water parameters were poor prior to the water change and then 90% was changed at once making the water parameters virtually could also cause shock. Going from poor water to pristine water can be just as shocking as going from pristine water to poor water.

    I don't know. It would be helpful to know what kind of condition those particular angels were PRIOR to the 90% water change. Maybe they were already not feeling the greatest and then the 90% water change proved to be too much?

    As for why the other fish are doing could be that the ones from that breeder had weaker genetics or something. It does seem strange that only the ones from that one breeder are struggling.

    Do you know how the fish were doing prior to the water change? Do you know what the parameters were prior to the water change? Have you compared your tap water PH with your tank water PH? Just some ideas to try and narrow down the cause.
  5. LakeMann New Member Member

    No, I unfortunately do not know the water parameters before. I previously would change 20%-30% once a month. I agree and assumed that it has to do with some form of shock from the significant water change. Is there anything I can do? The angel continues not to eat and is opening its mouth rapidly.

    I just checked the water parameters yesterday, temperature is good, one side has no lights and the other is lit, and I have plenty of aeration and hiding spots. I have not introduced anything new in the tank for months, so I doubt this is a parasitic/disease issue.

    Attached Files:

  6. bizaliz3 Fishlore Legend Member

    That isn't very frequent for water changes. Typically weekly is more ideal. So with small water changes monthly...and then a huge 90% water change, surely there was a big change in the parameters.
    How many water changes were done while you were away at school? long did it go without a water change?

    I am not really sure what you can do for him. Sometimes fish never bounce back after going through different types of shock. I am sure you are doing everything you can!!!!

    I am so sorry this happened!
  7. LakeMann New Member Member

    Ok thanks for the assistance though! I've culled the angel. No interest in breeding fish with low genetic fitness.