Goldfish Growth

  • #1
Hi! I currently have two calico fantail golfish in a 10 gallon tank. I know, too small right. Yes, I am aware of that. :] Unfortunately I just don't have the money or the space to buy a 30 gallon tank for my little buddies. At the moment they are 1.5" and 1" (including the tail) so they are still quite small. I keep my water crystal clear, I treat it with something I got from my lfs that gets rid of the chlorine, ammonia, and chlorammines. My tank is already cycled, the nitrates and nitrites are kept very low, and I vacuum the gravel once if not twice a week - removing between 25-35% of the water while doing so. I also just installed an air pump with a 10" bubble bar just in case the water had a low oxygen content. I've had them for a bit longer than a month and they seem to be doing just fine. I only feed them once a day and give them peas from time to time. I bought the tank before I knew about the whole 20gal for first fish and 10gal for each add, so I just went by the inch rule. I figure I have a bit of time before my fish need more room, but I was wondering if anyone knows how long it takes for fancy goldfish to grow? I will definitely start saving for a new tank but I want to know if I should take on a summer job(still in high school) to get a new tank or do I have some time before my fish grow?
  • #2
HI there,

I can't tell you when you'll need to buy a new tank or what schedule you should work to pay for it, but I can tell you that figuring out goldfish growth rates is a difficult thing. This is because goldfish apparently secrete a growth inhibitor, so their growth rate is affected by the size of their environment and the quality of their water as well as their genes. I've also read that early care has a profound effect on the lifelong growth of the goldfish, so what conditions your goldfish lived in when they were babies might play a role.

Estimates that I've seen for growth rates of common goldfish have ranged from around 1" to 4" in the first year, but fancy varieties may grow more slowly. I believe that the fancy varieties usually take at least a year or two (or three?) to achieve their full size.

Perhaps you can watch your goldfish for a few months and try to estimate how fast they are growing. While not a perfect solution by any means, this may give you an idea of when you'll need a new tank for them. Obviously, the goldfish would probably prefer the sooner the better, but you need to look out for your own finances too.

If I can make a suggestion ... the least expensive place I've seen to buy a tank lately is second hand, in the newspaper or an online marketplace like craigslist, from people who bought it and then didn't learn how to use it properly. They set it up, don't cycle, their fish die, and they decide they don't like aquariums. If you're willing to use a little elbow grease to clean up such a tank, you may be able to afford one sooner than you think!
  • #3
Well done in being such a good provider for your new fish! I only wish I was so well versed when I had my first fish tank
I think you do have some time before you will need a bigger tank- a few months most likely.

  • #4
All good advice ! Keep a watch on the water parameters to judge if you are doing enough water changes. You shouldn't have any ammonia or Nitrites and unless it is heavily planted Nitrates 20 or less.
Keep up the good work and get a larger tank as soon as possible.
  • #5
I was in the same situation as you, being in high school makes the financial part of fishkeeping tricky. I was at petsmart, and if all you need is a bigger tank they actully sell plain tanks with nothing but the tank for very cheap, I would definetly take a look at them if u have a petsmart near u!
  • #6
I think you should be fine with that tank for a while, I had 4 cichlids in a ten gal tank also and that's to be over stocked a few months didnt hurt them in my eyes, but I did up grade tank and they grew like wild fires from a 10 gallon to a 75 gallon is a big step. I also spent like $600 to set it up and still not done I want to get a new light and the one I bought is brand new its just not meeting my wants and needs in lighting the tank. I think you should be good for at least 2 months b/c if I'm right the fish grow faster when they have more movement from side to side and since they are in a smaller tank it will slow the growth. and for the vets in the site sorry is I put something wrong in here just trying to help.
Tigress Hill
  • #7
I have had my fantail goldfish Ponyo since mid-Febuary, and as of today she is three inches. Is this normal? My comets used to grow much faster.o
  • #8
I have had my fantail goldfish Ponyo since mid-Febuary, and as of today she is three inches. Is this normal? My comets used to grow much faster.o

How big was she in February? Hard to make a comparison with just one measurement...
Tigress Hill
  • #9
Sorry She was around an inch... 2 inches in 6 months? Seems rather slow to me.
  • #10
Well, she's tripled in size in 6 months. That's not too bad really in my opinion, my fancy goldfish grew at about the same rate.

My oranda and blackmoor grew at about that rate, whereas my bubble eye grew slower (probably due to the oranda and blackmoor outcompeting it for food).

What are you comparing Ponyo's growth speed to? Comets? Anyway, I wouldn't worry too much to be honest as she's growing. Also, different breed lines will probably have slightly different growth rates etc.
Tigress Hill
  • #11
Yes, I was comparing her to comets;D How long until she reaches full size do you think? I'm setting her up a larger tank that I mentioned in my other recent thread.
  • #12
Yes, I was comparing her to comets;D How long until she reaches full size do you think? I'm setting her up a larger tank that I mentioned in my other recent thread.

It's hard to say since their growth rate also depends on their tank size, water quality, etc. But I will venture a guess that she will grow a lot quicker once she's in the bigger tank.

To answer your question, people say they take anything from a year to two years to reach full size. I rehomed my goldfish before that, so can't speak from experience.
Tigress Hill
  • #13
Are lima beans a good food for goldfish?
  • #14
She doesn't seem to be growing as fast because the first year is more toward putting on a gut than it is putting on length for fancies. Really, she's growing at the same rate, just out, rather than than long
  • #15
It's true have you looked at her from above lately? I bet she's rounder than you remember
Tigress Hill
  • #16
Oh I definitely have noticed her rounding out, she had almost no belly when I bought her

EDIT:I just fed her half a lima bean. It was hilarious! After she was done, she kept trying to eat one random green pebble in the tank I took it out before she succeeded
  • #17
And you aren't sharing pics WHY?? *raises eye brow*
Tigress Hill
  • #18
LOL okay. Give me a sec
  • #19
One.... Times up! ;D
Tigress Hill
  • #20
Of course, she starts darting around the tank when it's photo time I had to take about 50 pictures to get these shots



  • #21
Aww how cute!
Tigress Hill
  • #22
  • #23
Hello everyone

I recently bought 3 "feeder" goldfish because I was convinced by my girlfriend to save them, I had a lonely danio left over from the fresh water crays I used to own (he was meant to be eaten!)

I now love these little fish, got the lonely danio another 5 of his own species to keep him from bothering the goldies, upgraded the tank to a 3 foot 40 gallon tank and have a 200L/H hob and a 400L/H internal filter plus plenty of live plants for the fish to eat and swim around...

I have heard that goldfish release a growth hormone into the water that will stunt them and stop them growing, I want to try and grow my "feeders" and give them the best life they can have!

Do constant water changes "dilute" this until I can make space for a bigger tank?
  • #24
I have never heard of the hormone being released into the water, but in general frequent water changes are necessary for goldfish as the have a large bio load.

Sent from my DROID RAZR HD using Fish Lore Aquarium Fish Forum mobile app
  • #25
I do believe that the whole hormone released into the water thing is true.
  • #26
It's not that there is a hormone that is released to suppress growth, it's that the growth hormone all animals possess is suppressed.

It is my understanding that if you are purposefully overstocking a tank, then keeping the water as pristine as possible will help in the effort to keep the fish growing and healthy. But this has nothing to do with removing some hormone that is being released.

In all honesty, the best advice is to not buy fish that you cannot properly keep. Lots of things can happen in life. Even with the best of intentions, things come up.

3 comets will need a very large tank. Not something that will be cheap.
  • #27
Thanks for the replies

How big of a tank is required?

I'm willing to up size again if needed, I thought 40 gallon tank would be a good size..

Would they be ok in the 40 gallon until they grow a bit bigger? As they are all only just over 2 inches
  • #28
A 40 breeder will work for a little while. But for 3 comets, j wouldn't get anything smaller than a 180 gallon for a permanent home.
  • #29
I don't want to get into an argument or be controversial but we have to put things into perspective, these are 'feeder fish', commodities produced by the billions in high density settings, born and bred in very 'dirty water' to be food for other fish. Once in the pet shops, they're also kept in high densities, only to end up in the bellies of other animals.

The few who make it out end up in small tanks or worse in fish bowls. So I think that the OP is making a good start with a 40g.

OP, keeping goldfish can be a lot of work, especially if the tank size is too small. Just try to get the biggest tank that you can afford.

Best of luck.
  • #30
My sister has kept her Comet goldfish in a 3 gallon tank since she got him about two years ago. After finding him being poorly cared for I decided to adopt him.
I've just purchased a 29 gallon tank that I will be setting up and preparing to move him in to.
My plan is to set up the tank with some plant life (I have read that fast growing plants are necessary for goldfish because they tend to munch on them), then move him and potentially a few more fish into the tank.
But I have also read that bigger goldfish will often eat smaller fish.
My concern is that since the goldfish is already over 2 years old, he will not grow any larger if moved in a tank more suited to him, and that any new fish placed into the tank will, and they'll end up eating him.
Would anyone happen to know if he will grow or not?
  • #31
He will still grow but not as much as they usually do in the first year
  • #32
I have a stunted one, expect maybe a half inch of growth every two months or so. It will likely be faster for the first 3-4 months, then slow down.
Mine really likes anacharis and Pennywort, and there should be enough living that some survives
  • #33
How much should I expect him to grow? I would say he is about three inches long right now. Not much bigger if at all bigger than when we got him
  • #34
Honestly, not sure. Mine is 5.", was stunned at 2" for two years. So 3" of growth in about a year.
My best guess would be the final length is going to be around 6-8"
  • #35
A 29 gallon tank is not going to last him for too long if he's a comet. Common goldfish like comets can get to over a foot long. Fish will grow to the amount of water they have; he'll probably grow a bit and then plateau out. I'd honestly think about getting a bigger tank than a 29 gallon.

As for plants, goldfish will munch but a lot of plants will be too tough for them. I have sword grass and anubias and my goldfish don't touch them. They peck at my hornwort a bit, but not as much as say something like anacharis.
  • #36
I think under the circumstances, 29 gallon is fine. One can always upgrade later.

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