Obese goldfish

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riri7022

Aquarium Advice Newbie
Joined
Feb 10, 2025
Messages
3
Location
Australia
I’ve had this fish for a while and recently moved it into a 70 litre tank. I do a 80% water change about once a month and will do 20% once every two weeks. It has a basic foam filter in the tank from Amazon and not much else. I dont check for ammonia or nitrate levels currently but would love more information on this. I can’t afford a testing kit at the moment but would be able to buy recommended solution if that will treat the fishes illness. I’ve been feeding it peas every other day and fasting it the other day because I’m scared of it growing in size.

I noticed about a week ago that my goldfish has blown up in size by an alarming amount. It’s showing symptoms of dropsy by its large shape, has become more lethargic during day but will still rush to get fed food. This fish has always been very active and was doing great when first moved into the tank about 2 months ago but has been doing a lot worse recently. I’m really worried and I’m not sure what illness it has or how I can resolve it. Any advice is appreciated.

I’ve attached some pictures for reference. Sorry if they’re blurry the fish moves pretty quick despite its size. One of the pictures I’m trying to show it’s hole because it looks quite big 😭
 

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Unfortunately even 70 litres is nowhere near big enough for an adult goldfish. What was it before the upgrade?

Do you know your water parameters? A monthly water change for a goldfish in a too small an aquarium is again, nowhere near enough. You might have needed that 80% water change a couple of times a week.

When goldfish are kept in too small an aquarium they release growth inhibiting hormones that stunt their growth and cause internal health issues. Throw in what's likely to be poor water quality too, and it's not a healthy environment to live in.

How big is the goldfish? An adult fancy goldfish at say 2 years should be about 8 inches.

I agree with your dropsy diagnosis, there looks to be some pineconing. This is the result of internal organ failure, and would be consistent with the conditions its been living in. Once the symptoms are visible there isn't very much you can do. I notice you are Australia based, where antibiotic treatment that might have an outside chance are vets prescription only. Do you have a vet that does fish you can consult? Its going to be expensive though, with no real prospect of being treated.

Sorry to say this, but I'd euthanise the fish.
 
Hey thanks for your reply.

I’m not sure what the water parameters are for the tank I didn’t have any of the equipment to check. I’d say the fish is about 8 inches or less from end to end. I can definitely go to a vet but I was hoping I could treat it myself as I don’t have the money. Also, if the fish can’t be treated I don’t see the point in going to a vet.

It’s horrible to hear that I will have to euthanise the fish but that’s what I was thinking as well. I’ve actually had the fish for 6 years and it was in one of those starter kit tanks before which is why I went for a bigger tank because I finally had the money to spend and didn’t want it to live miserably. It’s really tough to hear that it still wasn’t getting the care it needed, I watched videos and researched for a while to keep upgrading the tank so I thought I was on the right track.
 
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If you have managed to keep a goldfish alive for 6 years in a small aquarium you have done very well.

70 litres would be fine for a grow out tank until the fish was 4" maybe, but after that 100 litres minimum, 120 litres would be better for a fancy goldfish. And filtration rated for 150 to 200 litres. 50% water change every week is a good habit to get into.

It's just time and less than ideal living conditions catching up with your fish.
 
Hey, this is my final update.

After a lot of deliberation I decided to take my goldfish to the vet yesterday. The conclusion from the vet was that my fish wasn’t suffering from swim bladder disease but actually had a tumour in its abdomen which resulted in it growing to an extreme size. They also checked the water parameters of my tank and found that the water was actually clean and wasn’t the reason for my fish developing the illness but that it was most likely genetic.

After hearing all of this I made the decision to euthanise my fish. It was extremely hard but I didn’t want them to suffer anymore and their health was rapidly declining which would have resulted in their death eventually.

Once again, thanks for your advice. It was the push I needed to make a decision I was avoiding.
 
Hey, this is my final update.

After a lot of deliberation I decided to take my goldfish to the vet yesterday. The conclusion from the vet was that my fish wasn’t suffering from swim bladder disease but actually had a tumour in its abdomen which resulted in it growing to an extreme size. They also checked the water parameters of my tank and found that the water was actually clean and wasn’t the reason for my fish developing the illness but that it was most likely genetic.

After hearing all of this I made the decision to euthanise my fish. It was extremely hard but I didn’t want them to suffer anymore and their health was rapidly declining which would have resulted in their death eventually.

Once again, thanks for your advice. It was the push I needed to make a decision I was avoiding.
Sorry to hear but not surprising. Today's goldfish seem to be prone to tumors but usually they appear on the outside. If it helps, I think you made the right decision. (y)
 
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