Aggressive Fish / Moving to Bigger Tank

Hello everyone.

I've been struggling with this problem for a while and I'm not sure how to proceed. I have 4 common goldfish and one of them is being aggressive. He has been this way ever since the very start of bringing him from store. I had 1 single older goldfish and brought home 3 young goldfish. One of these young goldfish turned out to be aggressive.
Ever since the very start he would poke this original oldest goldfish to her side especially when food was at stake. He is now chasing, poking and harrassing all other fish in tank, not just the oldest fish.

I'm going to soon transfer them to a new bigger tank. They are going from 20 gallon to 40 gallon.
My question is, which fish should I move to a big tank first? The aggressive young fish to give rest of fish some relief?
I'm worried if I move the aggressive fish first, it will start establishing territories in new tank and once the rest of the fish are added, he will still remain aggressive or it will worsen.

I heard that fish form territories in tank. I would like the biggest oldest fish to be most dominant as it is the biggest. Does the order of adding fish matter?

Should I move the big fish first or the little aggressive nipper? LOL

I have tried the timeout in the bucket twice and it didn't help. I'm not ready to give the fish up either.

Appreciate all your help guys! )))

 

Hi! I keep goldfish too... Not to be rude, one common goldfish need at least 40 gallons each... and you have 4 in a 20 gallon. The lack of space may cause any animal to become aggressive, the one that is extremely aggressive could be a male, who are often more aggressive than females. i suggest you move the older fish to the 40 gallon, but I also suggest that you get a much bigger tank for all of your fish.

 

Sounds more like a young male acting like a young male if you know what I mean. If the aggressive one has what looks like white pimples on the gill plates and along the bony ray of the pectoral fins (google goldfish breeding stars) then he is indeed a male chasing the girls around.

Common goldies are not meant for aquarium life IMO, they are pond fish for a reason. They should be in tanks much larger than 20 or 40gals as they will reach lengths of 8in+ unless stunted in small aquariums. Of course loads of people keep common goldies in the average small tank and they do live for quite a long time. I simply do not view goldies (unless we are talking the fancy oranda types) as appropriate aquarium fish.

For the time being, I'd probably keep the problem male in the 20gal and move the others to the 40gal. Come spring I'd be looking for someone with a koi pond to give them to then switch to fish that are more likely to do well in the tanks sizes you have.

 

Hi! I keep goldfish too... Not to be rude, one common goldfish need at least 40 gallons each... and you have 4 in a 20 gallon. The lack of space may cause any animal to become aggressive, the one that is extremely aggressive could be a male, who are often more aggressive than females. i suggest you move the older fish to the 40 gallon, but I also suggest that you get a much bigger tank for all of your fish.

Hello guys! I appreciate your quick responses!!
Yes I am aware of the facts you stated.

Disclaimer: Keeping common goldfish was NOT MY first choice lol. I took them from a friend who kept them in neglect. I wasn't a fish keeper to begin with. I decided to take them off her hands so they don't suffer. I am doing my best for them.
And yes, I have plans of upgrading tank FURTHERMORE, lol.
Friend that kept them didn't provide them with anything at all. So whatever they have with me is KINGDOM lol.

About breeding. I don't think that is the case. As i said the young goldfish used to do that from the very start when it wasnt mature by any means. It doesn't have the white specles on gills now or ever.

Thank you again for your responses I wanna take care of them the right way.

 

probably just an aggressive fish then, some fish just have personalities like that...

 

Sounds more like a young male acting like a young male if you know what I mean. If the aggressive one has what looks like white pimples on the gill plates and along the bony ray of the pectoral fins (google goldfish breeding stars) then he is indeed a male chasing the girls around.

Common goldies are not meant for aquarium life IMO, they are pond fish for a reason. They should be in tanks much larger than 20 or 40gals as they will reach lengths of 8in+ unless stunted in small aquariums. Of course loads of people keep common goldies in the average small tank and they do live for quite a long time. I simply do not view goldies (unless we are talking the fancy oranda types) as appropriate aquarium fish.

For the time being, I'd probably keep the problem male in the 20gal and move the others to the 40gal. Come spring I'd be looking for someone with a koi pond to give them to then switch to fish that are more likely to do well in the tanks sizes you have.

Hello Demeter, thank you for responding
So you think the problem male should go to the new tank as last?

I will need to move them to new tank slowly as it is newly cycled tank. And can't add ton of bioload at once. So do you think I should add the oldest fish in there alone by itself?
And the aggressive nipper as last?

 

just introduce them slowly... one by one it doesn't really matter the order... test water parameters to make sure that they're okay before adding another fish...

 

just introduce them slowly... one by one it doesn't really matter the order... test water parameters to make sure that they're okay before adding another fish...

Hello F1sh. Thanks a lot for advice! Alright then, will do

 

if you are looking to get a bigger tank, you could settle on a plastic tote... there are some 150 gallon totes(which should be enough to house all 5 of your goldfish) out there that only cost $200, which should be(I think) around the same price as that 40 gallon of yours, it may not look as good, but hey, it gets the job done.

 

if you are looking to get a bigger tank, you could settle on a plastic tote... there are some 150 gallon totes(which should be enough to house all 5 of your goldfish) out there that only cost $200, which should be(I think) around the same price as that 40 gallon of yours, it may not look as good, but hey, it gets the job done.

Oh thanks a lot! Yes I've considered that too. From Tractor Supply they sell those black plastic ponds. I will consider that. I've been looking into buying super large 210 gallon tank in future. When 40 gallon won't suffice any more. Btw, I have 4 of them so little fewer

 

ahhh. my bad, i thought you had 5

 

If the aggressive one has what looks like white pimples on the gill plates and along the bony ray of the pectoral fins (google goldfish breeding stars) then he is indeed a male chasing the girls around.

NinaJ just a note: female goldfish can have stars (tubercles) too, and they can be absent on males. That's not really the most reliable way to tell.

Probably the best way to tell is the shape of their vent. Females' vents point outwards, males' are concave. However, I discovered the best time to check is BEFORE feeding, or during fasting. I found that many times, a goldfish's vent will change shape after feeding them, and sometimes a proven male can have an outward vent after he's fed.

 

NinaJ just a note: female goldfish can have stars (tubercles) too, and they can be absent on males. That's not really the most reliable way to tell.

Probably the best way to tell is the shape of their vent. Females' vents point outwards, males' are concave. However, I discovered the best time to check is BEFORE feeding, or during fasting. I found that many times, a goldfish's vent will change shape after feeding them, and sometimes a proven male can have an outward vent after he's fed.

Wow, I have never heard of any of this, great information.

 

Wow, I have never heard of any of this, great information.

Thank you! I guess the years did pay off

 

NinaJ just a note: female goldfish can have stars (tubercles) too, and they can be absent on males. That's not really the most reliable way to tell.

Probably the best way to tell is the shape of their vent. Females' vents point outwards, males' are concave. However, I discovered the best time to check is BEFORE feeding, or during fasting. I found that many times, a goldfish's vent will change shape after feeding them, and sometimes a proven male can have an outward vent after he's fed.

Hello JustAFishServant. Wow that's interesting information! I will try to notice it from now on. I read / watched on how to gender fish but I'm no expert and can't be sure.

 

Hello JustAFishServant. Wow that's interesting information! I will try to notice it from now on. I read / watched on how to gender fish but I'm no expert and can't be sure.

No problem! Gendering goldfish isn't easy, especially egg-bellied (aka "fancy") breeds. Yours are hibuna (aka wakin, common, comet, flat-sided, single-tail, slim-bodied, long-bodied, wild type, etc.) They're a little easier to tell apart. Typically, female slim-bodied goldfish are wider. Look from above - if the body is wider than the width of the head, it may be a female. If it's thinner or the same width of the head, it's likely male...provided they're not obese

 

No problem! Gendering goldfish isn't easy, especially egg-bellied (aka "fancy") breeds. Yours are hibuna (aka wakin, common, comet, flat-sided, single-tail, slim-bodied, long-bodied, wild type, etc.) They're a little easier to tell apart. Typically, female slim-bodied goldfish are wider. Look from above - if the body is wider than the width of the head, it may be a female. If it's thinner or the same width of the head, it's likely male...provided they're not obese

thanks a lot, haha No, they are not obese. I have a hunch that I've got 1 female and 3 males. Yeah, I know it's not ideal. But again, I'm not an expert and not sure the young fish reached adulthood yet. I know it's easier to tell once they are adult.

 

thanks a lot, haha No, they are not obese. I have a hunch that I've got 1 female and 3 males. Yeah, I know it's not ideal. But again, I'm not an expert and not sure the young fish reached adulthood yet. I know it's easier to tell once they are adult.

I've had several males together without issue. With more males than females, you may see aggression. Then again, nothing's for certain