View Full Version : Why does new goldfish bites old goldfish?

02-12-2010, 07:21 PM
When new goldfish are introduced to the tank with old goldfish, why does the new goldfish bites the old goldfish, even if it is the same kind of goldfish?? What should I do in order to prevent this from happening?

02-12-2010, 07:23 PM
Are the actually hurting the new one? How big are the old ones and the new ones?

Goldfish don't really attack each other, or anything for that matter. They could just be deciding if they can eat it or not. That is about the only thing they care about most of the time.

02-12-2010, 07:57 PM
There are 2 cases happened to my goldfishes, for which, when new ones are introduced to the old ones, the old ones died (all died).

1st case:
I bought 3 pearl goldfish last week. It was introduced in a brand new aquarium, they are doing fine for 3 days until 5 new pearl goldfishes of the same size were introduced into the tank with the other 3 pearl goldfishes. Then each of the old pearl goldfish died in 3 consecitive days... Based on their outlook appearance (the old ones), they are not as active as the new ones, but they look quite healthy. So, don't really know the reason why they died??

2nd case:
I have my old ones (5 pearl goldfish) living for almost 4 yrs. before they die. I bought 3 new goldfishes (2 red caps and 1 ryukins), and introduced them with my 5 pearl goldfishes. Actually, the size of the new ones are smaller than the old ones. The first few days, they get along well but after quite sometime, the new ones start biting the old ones' fins, until later I found out, all of my old ones died :(. They all died just within a week :(.

I was figuring out the problem why after introducing the new goldfishes, my old goldfishes will die... but until now, I haven't found a reason yet. Please help! Thanks!

02-12-2010, 08:08 PM
what size tank/pond are you putting them in? The goldfish may have just died and gotten eaten/chewed on.

fish will eat dead or dying fish, no way to stop that. Even if they are not dead yet, if they are very sick they will get chewed on.

Do you have any water testing kits?

02-13-2010, 08:04 PM
For the 1st case, the aquarium size is: 18" x 11" x 12". The size of the fishes are all approximately 1 inches length.

For the 2nd case, the aquarium size is: 50 gallon. It was originally 5 pearl goldfish (size around 2-3 inches), and when 3 goldfishes (2 red cap and 1 ryukin, size around 2 inches), all the 5 pearl goldfish died consecutively.

No, I don't have water testing kit. But the solutions for anti-chlorine were put in the aquarium for 1st time change of water.

02-13-2010, 08:08 PM
For the goldfishes that are selling in the store, how come they all look healthy and active, even if the aquarium has very small space for them to swim? Do you have any idea what do they usually put in the aquarium??

02-13-2010, 09:03 PM
You said you have had your old fish die twice after adding new ones...

Did you quarantine the new ones first or just dump them in the tank with the old ones? Also did you dump the water that was in the bag with the new goldfish in your tank?

Chances are the goldfish you are buying from your local store are sick/dying and that is why they are dieing.

02-13-2010, 09:03 PM
For the goldfishes that are selling in the store, how come they all look healthy and active, even if the aquarium has very small space for them to swim? Do you have any idea what do they usually put in the aquarium??

Its not a case of oh don't they look healthy, its a case of quick take out the dead and/or dying ones or customers won't buy the rest. Its sad but true :scry:

02-15-2010, 01:00 PM
No, I did not quarantine the new goldfish before putting in the aquarium with the old goldfish. But I do dump the water that was in the bag with the new goldfish before putting inside the aquarium. How should I quarantine the new goldfishes? And for how long?

For the selection of goldfish, how can I know I am selecting the ones that are healthy? Are there any things I need to observe as a whole? Like for example, the color of the aquarium water inside the goldfish, etc....?? What are the preference?? Co'z when I choose the goldfishes, I look at the goldfish individually and choose those that are very active inside an aquarium that are in the shop. But one thing I noticed, when I bought the pearl goldfishes, the water of the aquarium is colored yellow. Is that good or bad? Is it because they are conditioning the water, that makes the water inside their tank looked yellow??

Thank you for any informations provided :).

Lady Hobbs
02-15-2010, 02:02 PM
You need to read about cycling first. Links are at the bottom of this post and then you need to look in this section (where your post was moved) at the red stickie thread as to the size goldfish get. Dechlorinator needs to be in all your water. When you fill the tank and in every water change.

02-15-2010, 10:09 PM
You need to do quite a bit of research. Check out Lady Hobb's signature for some important links.

As for them nipping each other, they're likely both males, and thus are just having a dominance schuffle. And sometimes different breeds of goldfish taste the other kinds trying to figure just what kind of thing they are - edible? Alive? Etc.

Yellow tank water either means that the tank is highly dirty and you should stop going to that petstore, or they were treating with a common fungicide - in which case you should still avoid the fish in that tank.

02-19-2010, 04:53 PM
IF your tank isnt cycled , all of your fish may be sick. So thats a reason why the new ones "no sick" will attack the other ones,make sure to get a test kit, or take water to ur LFS and have them check it out for u.
I had this happen also with a ryukin and i ended up putting him in a different tank , im planning on putting him back ones i set up my new aquarium.
And they will be always get along at first , until the fish gets used to the new home and see how the other fish are.
Make sure your tank is cycled , and if it isnt try and take him(them) back to the store, maybe do a fishless cycle or at least take back the new ones cuz u ll just end up with more dead fish and new sick fish.

02-19-2010, 05:03 PM
The first time you said it was a new tank. So my guess would be they died becuase they where in an uncycled tank. Get a liquid test kit. API is a good brand and test your water. Do you do water changes? How much, how often? Goldfish are messy fish and produce a lot of waste, which turns to ammonia. Ammonia is toxic to fish so if you are not doing large weekly waterchanges you will have problems. And as far as the petshops having large numbers of fish in thier tanks, remember they are only holding them for a short period of time, and they do have deaths.