Fish is really happy and eating one day, dead the next

A few days ago one of my two goldfish died. It had been acting weirdly for a while, so I saw it coming. A few minutes ago I came home to find my other fish dead in the tank. It seemed fine this morning and it ate the food I gave him. Did it die because of loneliness, or something else?

Hi Ilona,
how big is your fish tank? Do you have a filter system in your aquarium? How much and how often did you feed your fish?
Most goldfish die in undersized, unfiltered fish tanks to ammonia poisioning. Sometimes they die to overfeeding.

They will never die to loneliness. They do not even get lonely since they are not school fish.

yes ...that is happen to my fish too...dunno what happen suddenly death the next day

There are so many things can happen. Without providing some detailed information of your aquarium set up, as well as what you have been doing, it is impossible to pinpoint the cause of the fish deaths. I can't help you at all without knowing more facts.

Goldfish are very fragile and slight changes in some parameters in their environment results in death. For example, they have zero tolerance to ammonia and nitrites and are poisoned by them. Other causes include oxygen deprivation associated with low pH, supersaturated gases, enclosed tank and lack of proper water circulation. Nitrate poisoning may also have caused the death or harmful bacterial infection caused by low levels of O2, improper maintenance and poor feeding routine. Finally, too much feeding, high water temperatures as well as chemical poisoning may have caused the death.

(04-23-2016, 04:02 AM)remnant Wrote: Goldfish are very fragile and slight changes in some parameters in their environment results in death. For example, they have zero tolerance to ammonia and nitrites and are poisoned by them. Other causes include oxygen deprivation associated with low pH, supersaturated gases, enclosed tank and lack of proper water circulation. Nitrate poisoning may also have caused the death or harmful bacterial infection caused by low levels of O2, improper maintenance and poor feeding routine. Finally, too much feeding, high water temperatures as well as chemical poisoning may have caused the death.

Goldfish is actually quite hardy compare lets say tropical fish. It is hard to get them killed under normal circumstances.

No fish should be in an aquarium with ammonia and nitrite (both readings should be kept at 0ppm), but they will not immediately drop dead from low concentration. So the zero tolerance is false.

Die from lack of oxygen is only likely if the aquarium is too small with very little water surface area for gas exchange with the atmosphere.

Nitrate is harmless. Although it is believed that extremely high concentration of nitrate can lower the immune system of the fish and make them easier to catch diseases and parasites. Usually we fish owners keep the nitrate below 40ppm. Only for more fragile fish (goldfish are certainly not one of them) we aim for below 20ppm nitrate. Of course the lower the better. Since nitrate is not toxic, there is no such thing as "nitrate poisoning".

Overfeeding is one of the most common causes for trouble in an aquarium, but it is an cause for trouble not the direct reason for fish's death. Overfeeding can result in too much leftover fish food in the cycle, and it can result in ammonia spike in the aquarium, and fish can
die from ammonia poisoning since ammonia is toxic.

High temperature is usually not a problem for goldfish. They can adapt to fairly high and low water temperature unlike tropical fish. Too high temperature while lack of an air pump might cause a lack of oxygen in the water.

Low PH isn't a problem either unless it took place too quickly and the PH swing is too big. Most fish can get used to the change in PH if it happened slowly.

Like I said, there are too many possibilities and there is no way for any of us to find out what's going on until the OP give more details.

Well, you said that your one fish had been acting weird for a while. Was he floating upside-down a lot, or swimming in circles? Was he just very sluggish, swimming slowly and acting uninterested in life? Was his body bloated? Did he scrape his sides against the walls of the tank a lot? Was he simply swimming to the top to gasp at the surface? Acting weird covers a lot of territory with goldies. Give us some idea of the symptoms and we can help you a lot better. Goldfish are social creatures but I've never yet seen one grieve itself to death. The chances are really good that your second fish died either from the same thing that affected the first one, but just didn't display the strongest symptoms, or the second fish had some other condition pop up suddenly at the same time that the first fish finally succumbed. Now that both fish are gone, this is a good time to clean the tank thoroughly, including filter media, tubing and any 'toys' that exist in the tank environment. Also, take out any live plants and give them a good rinsing in sudsy water, then rinse in clean water. Clean or replace the bottom media if any is present, such as rocks, pebbles or sand. Start fresh with clean water, clean filter, clean everything and allow the tank to cycle for a week or so. Some may suggest a month, but either works. Don't buy fish again until you have a clear idea of what caused at least the first death and can do something about it should it happen again. The symptoms I've described above are all legitimate goldfish disease symptoms, and many of them can lead either to permanent disfigurement or death. You can go online and google the symptoms exhibited by your fish and see what comes up as a match. Then you can learn how to deal with it if it pops up again. By the way, this may have already been mentioned, but goldies love cold water, so don't use a heater in your tank. Water that is too warm can make the fish act oddly because they are stressed. Stress in a goldfish almost always leads to disease, so that's something to watch out for.