Goldfish Keep Dying Suddenly?

Topic: I know this isn’t related to guppy fish but I also have a goldfish tank. My goldfish keep dying one by one Suddenly. I need some help figuring out what is wrong with my tank.. or what’s going on. Thanks for your time.


*Awarded Answer
Posted by Sarah B: The biggest reason Goldfish die is because of aquarium size mixed with what filter you have on the tank. The smaller the aquarium the MORE powerful filter you need. If your using a hang on the back filter I would highly suggest you buying the best one designed! It’s the AquaClear 110 series. It’s been the best for a long time and will help keep up with your goldfish (which are super messy). Here is a link to Amazon:

AquaClear 110 Aquarium Power Filter - for 60 to 110 Gallon
List Price: $79.97
Price: $79.93
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Posted by Jason B: Help! My small goldfish died and i didnt know..what the problem is..she seems healthy yesterday but i saw her today floating ..dead the water is clean …

  • How big is the tank? How often do you do water changes, and what %? Are there any other tankmates?
  • The tank is large and i did a 50% water change every two weeks.
  • How big is “large”? Do you know the amount of gallons or litres it holds? And are there any other tankmates?
  • Also – how long did you have your fish & if it relatively new for you – was it quarantined for observation & flukes treatment when you got it.
  • first – I am sorry you lost the little guy. I am not an expert, but considering it was a new fish – if the water parameters were OK – it is possible something was wrong with the fish. I have 2 tiny guys in 25g, cycled QT & as messy as they are – the amonia & nitrites are zero & after a week, the nitrates barely go up to 5ppm…
  • Well, I’m just trying to help. Some people don’t know you aren’t supposed to change too much of the water at once, or it will upset the balance of beneficial bacteria. I only change about a tenth or so at a time, once a week or two weeks.
  • No, it won’t. Water changes do not affect the cycle – your water changes are far TOO SMALL. 50% weekly is an absolute minimum. More is better, so I recommend increasing those. Such small water changes are a recipe for disaster. Bigger will not harm the beneficial bacteria, as the bacteria is not held in the water column.
  • Some people change almost all the water. I was just saying you shouldn’t do that. And I don’t see how there’s any disasters impending. All my fish have been doing fine for half a decade.
  • The only time I ever had unhealthy fish was before I learned to not change too much water, before I did research. Now, ten percent is the very minimum, and in reality I change about 25% if it’s been two weeks, but I was emphasizing the fact that small changes are better and I stand by that, but you also must have the proper Eco system for that, with real plants and snails. Lakes don’t get water changes. I have a natural environment that recycles much of the waste.
  • I do 80% or 100% once a week and my cycle is still going strong. Beneficial bacteria lives on the surfaces of the aquarium, so gravel, ornaments, filter media ect. But it is not free floating in the watercoloumn. This is why large water changes are doable without harming the cycle.Waterchanges also help oxygenate the water and replace mimerals that had been used up by the fishies.

Posted by Darren Z: I buried my goldfish yesterday. Didn’t think I would be sad about a fish dying, but Seabass brought a lot of entertainment to my tank. Got him when he was as small as my Glofish and he quickly grew into his name. He learned feeding routines and at night time would go to the back corner of my tank and take my algae eaters wafers, hide them and guard them. Hope he’s swimming freely and stealing all the algae wafers wherever he may be… We’re gonna miss him, but our cat Skibby is gonna miss him the most.

I can’t help but blame myself for this loss. I was poorly educated when someone gave him to me. Read up on goldfish care: got him in a bigger tank. Then I upgraded to a 30 gallon. Recently I noticed damage to his scales so I posted on this page. A kind lady suggested if I had any kind of sucker fish that might be the culprit. It was the next day I witnessed my algae eater sucking on Seabass. I hopped on Craigslist and got a new tank an hour later. Despite my best efforts Seabass lost his will to live and I am so upset with myself about it. I now know better than to keep my goldfish with certain others so his death was not in vein, but it is a tough one for me to swallow.

  • So sad. I’ve not had a dish die but I know it will hurt. It’s surprised me how attached I’ve become to them.
  • Him and my algae eater (Earl Sinclair) are the only 2 with names so I have definitely become more attached to them. I’ve lost a few Glofish when I was a newbie and it stunk but this one was real rough. Seabass had the biggest personality. My tank is boring without him 😿
  •  😺thank you. I’m gonna have to give myself a little time lol. I want a bigger tank than the hospital tank I got for Seabass. In time I will have another Goldie!!

Posted by Julie H: I’m just looking for advice. This is my tank the two goldfish I had inside died. I’m thinking now it was because they were unsuitable for the tank? They also had some sort of fungus and white spot. Is this tank no good? What type of fish could I put in here. My little boy loves watching the fish and my partner is also in the process of building a pond, thanks.

  • The tank is generally too small for goldfish sadly :/ you can use the tank again don’t worry! They probably developed the diseases due to stress and water quality. I recommend getting a heater and maybe betta their not complicated to care for at all! Also if you do get betta make are the fake plants don’t scratch the fins.
  • That’s debatable and in the Uk 15L is a general minimum although the British association regulating labyrinth fish suggests 12L.
  • Your fish aren’t well/are dying because the tank is much much too small hun 🙂 if you want to keep that tank, try getting a beta or maybe search up tank measurements that are okay for certain tropics once you find out the capacity. if you want to keep those you would have to upgrade the tank to about 60 gallons, as they both look like single tails, though one may be a fancy tail in which case you would need 55 Gallons 🙂
  • I’m assuming it has no filtration source??, they also don’t need heaters as they are cold water fish. One fancy goldfish will require at least 20-30 gallons and 15-20 additional gallons per fish. For this “bowl” I would think a betta is your best option.
  • I had one of these as my first tank, defo no good for goldfish. I use it now as a grow out tank or qt my is 60 litres ypu can get them smaller though.
  • I don’t care. You can probably find them much larger. The point is if you tell folks they can use bowls to hold fish then some people will think they can use small bowls.
  • I’d like to point out that I suggested a sponge filter. I understand the frustration. I had to leave the betta group I was in because telling someone it wasn’t ok to keep a fish in a bottle was considered tank bashing. I get just as angry, and I understand the bowl thing, but all we can really do as onlookers is make the suggestion, and give information. People will then do with it what they will, and often…I just stop following the post. It’s all you can do.

Posted by Nick G: Unfortunately- without a proper necropsy, definitive information about water parameters, habitat, and other background information we cannot tell you why the fish died for certain. We can just guess.
I am sorry for the passing of your little guy.

  • Is this a serious question? Tank size, temp, instead of saying the params are okay tell us what they are, other fish in the tank, how long was it set up before adding fish, like, literally any details. Its not that hard.
  • She’s not being impolite. She’s trying to get answers that you are apparently hesitant to give out, in order to help you figure out why your fish has passed, and hopefully prevent another from dying unexpectedly in the future.
  • We can’t help unless we have all the details. Any time people post and ask for help without giving details they are ALWAYS asked for more details to help narrow and give a better suggestion about what could have happened.
  • With the amount of help posts on here that either give details or have been asked for details, I’m surprised people still have it go over their head that we NEED DETAILS to help the fish, and you, figure what’s wrong.
  • Was it hard to give those details? So why so hesitant. What was it acting like before it died, other fish showing symptoms, etc etc are also helpful. Those are details that are helpful as well.
  • it seemed pretty clear to me what you were asking, and a fare question. There may be people on this page that could see some sign of illness on the body of the fish that would explain the death. It is good to ask, as others may spot something you could not and may help in care of the fish you keep and those that others keep.
  • I’m sorry for your loss!
    Unfortunately there’s no way to tell cause of death from a photo alone in most cases. We also need to know details like tank size, tank mates, water parameters (Ammonia, nitrites, nitrates, the exact numbers for these and whether you used strip or liquid to test), water change schedule, and how long the tank has been set up.
    With information like that it becomes a lot easier to narrow down cause of death!
  • if the tank and water are all good and all other fish are healthy. and no one can spot an obvious thing from the body of the fish, then it may have had a reason to die that was out of your control and nothing that you could have changed.