Goldfish dying suddenly

Question
QUESTION: I have had a two instances in the last few months where an oranda has died overnight.  This happened this morning as well.  Very distressing as they were my two favourite fish. I am really perplexed.

In both cases the fish was perfectly fine one day, bouncing about the tank being jolly and sociable, with zero signs of illness, and the next morning I have found it dead.

Both fish were 2-3 years old.  The only coincidence in both cases is that it happened the day after I did my tank cleaning and weekly partial water change.  I change about 20% of the water.  I always ensure the water going back into the tank is the same temperature.

This morning I checked the water parameters and all good except ammonia which was 0.25.  Nitrate was 40.  PH 7.4, Nitrite 0.  I again did a partial water change this morning to correct the ammonia level.

I really don't know what is happening as there are no outward signs of illness.  All the other fish are very well.  I keep 11 goldfish in a 100gal tank.

I very much appreciate your help as I am wondering if I am doing something wrong

Thanks so much
Kind regards
Mattie

ANSWER: Hi Mattie,
Oh, I'm so sorry to hear that. :(

Have you tested your tap/source water? Do you always make sure to add plenty of water conditioner to the new water?

Its a dangerous situation to have even traces of ammonia in your tank. And it could be from your tap water. Sometimes people encounter this problem a lot. Especially when the water conditioner they use eliminate chlorine and chloramine but they do so by breaking the chloramine/ammonia bond but what happens is it leaves ammonia in the water as a result. And some tap water sources do have an ammonia and even nitrite and nitrate reading. The best thing to do is use a water conditioner like Amquel+ or Prime to get rid of these toxins in the water when doing a water change to make sure you aren't unintentionally adding toxic water back into your tank.

Its always possible something may have caused the 'biofilter' to crash--in other words, the bacteria have died off in great numbers which in turn causes the ammonia spike. Water changes, testing, and using a water conditioner that neutralizes ammonia are your best bet in battling a condition such as this until the aquarium can become balanced again and established.

Best of luck and I do hope this helps!
Karen~

---------- FOLLOW-UP ----------

QUESTION: Hi
I now have three fish ill and I think they have septicemia lots of red patches and redness at base of fins and on fins.  I purchased some tetracyline today and hopefully this will help

Thanks so much for your help - will keep a check on the water conditions

Answer
Oh that's a shame!

I really hope you can get them better.

Because Septicemia is primarily a bacterial infection in the bloodstream feeding foods soaked in antibiotic have been known to help the best. Or Jungle Anti-Bacteria Medicated Fish Food
Best of luck!!!

Let me know if anything comes up!