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Anna, Pet Expert/Biologist
Category: Pet
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Experience:  40 yrs.: herps, pocket pets, rabbits, poultry, dogs, horses. Biology degree. Vet assistant.
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My grandson won a common goldfish about 3 yrs ago. Named him

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My grandson won a common goldfish about 3 yrs ago. Named him Goldberg. He's very active and seems to be very healthy still to this day. Shortly after we got him, we thought he should have a friend and got him a little white (goldfish) with an orange spot on his head out of the feeder tank at the pet store. It was a mix, it had a wider head and long tail fin, he named that one bomber. They got along well and then about 5 months ago bomber died. We went out after a couple weeks and got another one, because we feared goldberg would be lonely. Within 2 weeks the new fish died. We tried another one, same thing, within 2-3 weeks it died. We tried another one and this one lasted almost a month and it died. I watched them very closely because I have heard that one can bully the other, but he seemed to really like them. The new one's would follow Goldberg around, they hung out together, both ate well and they even slept side by side at night. He never showed any signs of aggression toward them. The newbies didnt show any signs of illness until 24 hrs before death. At that time they would get listless and hang out at the very top of the tank or the bottom for a day and then die. The last one we tried died 3 days after cleaning the tank, but with the others, that was not the case. Should we just keep him by himself?


I apologize that no one has responded to your question sooner. Different experts come online at various times. I just came online and saw your question. My name is XXXXX XXXXX I'm a biologist with many years experience keeping fish. I'm sorry to hear of your goldfish problems. Some additional information will be useful.

How big is your tank?

At the times when you've had two fish in the tank, have you ever tested the water? If so, what were the results for ammonia and nitrites?

Did any of the fish ever have red streaks (like blood vessels) on their fins or tails?

Thank you.

Customer: replied 3 years ago.

I've never tested the water, we have a 5 gallon tank with filter and aeration and our original goldfish, goldberg is 3 inches long. The other fish were approximately 2 1/4 - 2 1/2 inches long. They've never had any red streaks on them other than getting listless approx 24 hrs before dying never exhibited any unusual behavior and were still eating. They looked just like the day we brought them home. None of the other fish were common goldfish, which I guess that is what he is. He doesn't have the fancy long tail, he's torpedo shaped and was won at the carnival. The first one that lived with him that I mentioned before (bomber) lived for over 2 yrs.


I've always done 10 percent changes once a week and then every 4 wks I take a gallon or so of the existing water out and put it in a glass bowl, then take the tank, rinse the plants, tank and decor and just wipe the tank out with a paper towel. Never using any type of soap or cleaner. I use the water conditioner for goldfish and feed them regular goldfish flakes once a day.

The other two fish that have died were goldfish, but one was a speckled (like a calico cat) although it was not one of the expensive ones it cost $2.00 and the other was bright orange and white with markings similar to a clown fish but again only cost $3.



Thank you for getting back to me. The biggest problem is that your tank isn't big enough for two goldfish. I'll explain. Goldfish produce a tremendous amount of waste for their size. It used to be recommended to have one gallon (about 4 liters) of water per inch of fish. that still holds true for tropical fish, but not for goldfish. There are various recommendations, ranging from 2 gallons (8 liters) per inch of fish to 30 gallons (about 113 liters) per fish, regardless of size. So, even going with the minimum recommendation, Goldberg is ready to be moved into a larger tank. As he grows, he'll need more and more room, and if you want to keep more than one fish, you'll need an even bigger one. I’ll share my own experience with 18 inches total of goldfish (3 fish). They are in a 90 gallon tank. I have an undergravel filter, a hanging filter, and a powerful canister filter. It takes all three of those filters to maintain perfect water quality. Regardless of tank size, frequent water testing is needed.

What probably happens is that w hen you introduce new fish, ammonia and nitrites build up in the water. When that happens, the weaker fish will die first. New fish from the pet store are often not in the best of health, so it makes sense that poor water quality would affect them before Goldberg. After the new fish dies, your water changes and cleaning improve the water, keeping Goldberg healthy. Chances are the first fish you got lived longer because Goldberg was smaller then, and it took longer for the water to become toxic.

I suspect the water quality is never good, but isn't bad enough to make Goldberg ill. At 3 years of age, he should be bigger than 3 inches long. Mine usually reach 3 inches by the time they are one year old. When conditions aren't perfect, growth is slower. That being said, you have done much better than most people do with goldfish. Few goldfish live to be more than a few months old because they are kept in bowls, not tanks. But, the time has probably come to upgrade to a larger tank for Goldberg. Goldfish are somewhat social, but they also do well alone. If you want to keep only Goldberg, I would get at least a 10 gallon tank (and expect him to outgrow that in a couple of years). If you want to add a second fish, go with 20 gallons.

When setting up a new tank, there is a process called cycling which you need to be aware of. The nitrogen cycle, in which ammonia from fish wastes is changed to nitrites and then nitrates has not become established. That results in changing levels of ammonia and nitrites and puts a lot of stress on the fish. It also reduces the amount of oxygen the water can hold, and the fish will often gasp at the surface. cycling is very hard on fish. Some pet stores recommend making the fish suffer through the process, but often, they will die. There are other ways to cycle a tank. The following website gives detailed instructions and also explains cycling in depth. It will help you understand what happens.

Once the tank is cycled, we never want to change all of the water. That destroys the good bacteria, and the whole process has to begin again. Weekly water changes of 10%, along with vacuuming the gravel with a siphon, are the best cleaning measures.

The best thing to do would be to get your new tank and cycle it according to instructions on the link I gave you. Leave Goldberg in his present tank until cycling is complete. Then, if you want another fish, move Goldberg to the new tank, but leave the old tank set up. Any time you bring a new fish in, you risk introducing a disease. It's best to quarantine new fish for 30 days. If the new fish is healthy after that, it can be put in with Goldberg.

If you have more questions, let me know in a REPLY. I hope that whatever you decide to do it will work out well for Goldberg and other fish you get.


My goal is to provide you with excellent service – if you feel you have gotten anything less, please reply back, I am happy to address follow-up questions. Please remember to rate my service only after you have all the information you need. Thank you!
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