Goldfish Suddenly Dies
I HAVE A GOLDFISH THAT WAS IN A POND. IT'S NOW IN MY LARGE 120L TANK IN THE HOUSE ALONG WITH ONE OTHER GOLD FISH . IT WAS IN THERE FOR JUST OVER A YEAR BUT DIED YESTERDAY. I WOULD SAY IT MUST BE AROUND 12 YEARS OLD MAYBE 14 APPROX.
THE PH IS GOOD AND NOTHING DIFFERENT.
EXCEPT THAT I PUT A NEW FLUVAL 3 FILTER AS THE ONE IN THE TANK STOPPED WORKING THAT IS FOR THIS SIZE OF TANK ON 2ND FEB 2020.
24 FEB DID A WATER CHANGE AND ALL WAS WELL. NOT SURE WHAT WOULD CAUSE THE FISH TOO DIE WITHOUT ANY VISIBLE SIGN .
WOULD YOU KNOW WHAT MAY HAVE CAUSED THIS ?
There can only be three reasons for your Goldfish to die suddenly:
1. Old age
2. Water conditions or
3. A physical mishap.
Although not a great age, your fish at 12-14 years old was not young. You don't know the conditions it was raised in early in its life, nor do you know its genetic makeup regarding lifespan of the parents. Many factors determine how long a Goldfish will live for such as diet, size (stunting), variety and water temperature.
To keep a Goldfish for 14 years, you are doing better than 99.99% of Goldfish keepers.
Having said that, you said your water pH was fine. Did you test for ammonia?
When you replaced your filter, I assume you used the old filter media, and didn't start with new.
I ask because new aquarium setups with un-cycled filters last between 2-4 weeks, then a massive spike in ammonia occurs and fish start dying.
You mentioned you did a water change on the 24th. Was that a complete change or partial?
If it was a complete change, then we can eliminate water condition as a cause. If it was partial, there could have been enough ammonia left to cause stress. 0.5-1 ppm (parts per million) is enough to cause stress.
If you haven't changed the water since your fish died, test it now for ammonia, nitrites, both should be zero, and nitrates which should be below 40 ppm.
The third option of a physical mishap would be something like either a child or pet harming the fish or, the fish choking on a pebble. I have lost several fish from choking.