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View Full Version : Do goldfish only grow as big as the tank allows?



Ratlova30
04-28-2010, 4:19 AM
So I have this 4" goldfish that I believe to be comet. When he was a baby a former fried had bought him from a pet store to feed to her salamander and he got lucky and grew too big for the salamander to eat him. So at four inches my former friend was desperate to get him out of her salamander tank and being the good pushover friend that I am got stuck with him:rolleyes:. I've had him for about 6-8 months now living in a 10 gallon tank and he hasn't grown at all.

The other day I was talking with a friend that has a 55gal with some pretty huge ryukin goldfish in it and she said when she was a kid she had a 10gal with a couple little fantail goldfish that never grew and when I was a kid I had fantail goldfish in a 5gal and they never grew, I think I had them for about 5yrs before they died.

Is it possible that a goldfish will stop growing if the tank it resides in isn't big enough to support it's growth? I figured I'd find him a new home once he got too big but he hasn't grown and he fits quite perfectly in the tank. Thanks

londonloco
04-28-2010, 7:24 AM
It's not the size of the tank, it's the water quality that affects the growth of fish. Discus breeders change 50% of the water daily to get optimum growth of their discus fry.

Ara
04-28-2010, 8:12 AM
I would definately recommend upgrading your tank as soon as you can...


Goldfish can be stunted by the size of their tank, definately. This is likely why comet is not growing. Theirs bodies naturally want to grow... but their growth will stop if their tank size is too small, which can cause internal problems... skeletal and internal deformities will often occur as a result and lead to a shorter lifespan for the fish.

The smallest tank size recommended for a single goldfish is 20-30 gallons. Some places say 20 gallons + 10 gallons for each additional goldfish, but others say 55-100 gallons minimum.. but I would suggest an absolute minimum of 20 gallons, especially since your fish is already 4 inches, he is too big for a 10-gallon.

Good luck!

platytudes
04-28-2010, 8:14 AM
They've done experiments with trout, keeping them in small tanks and keeping fresh water flowing continuously. They grow until they literally can't turn around in the tank. There's also an experiment that David Boruchowitz (author and editor in chief of TFH magazine) did called the 5 gallon oscar tank with 12 oscars in a 75 gallon tank - there's more here if you're interested:
http://www.monsterfishkeepers.com/forums/showthread.php?t=228389

So as LL said, it's really the dissolved organic compounds (more the metabolites, hormones, etc. but also the measurable aspects of water quality like ammonia, nitrite and nitrate) in the water that drastically slow or even stunt the growth of fish. Some seem to stunt more readily than others.

You should still try and rehome the fish, stunting ensures the fish will die a premature death. I understand how one could think, "Boy, that 25 cent fish was going to get eaten, but it lived and now here it is in a 10 gallon tank, that's a lot better than ending up as dinner!" but put aside the monetary value and random 'feeder' designation that we put on comet goldfish...they are basically the Humane Society mutts of the fish world.

fishiefishie
04-28-2010, 8:56 AM
My nephew won 2 goldfish at a fair in town 3 years ago. I had a spare 10-gal tank layig around so I gave it to them. My sister kept the tank immaculate, water fresh, etc. Just before this spring came they were both about 5" long, beautiful. We were waiting for the water to warm up outside in my pond and were going to transfer them there. Well, wouldn't you know it, they both ended up getting ill and dying within just a couple days of each other, just before we were going to moving them.
Moral is, they will not grow as large as they should, but even if they do keep growing, they will have a VERY short life. Goldfish can live upwards of 20-30 years. Keeping them alive only 4-5 seems pretty cruel.

petluvr
04-28-2010, 9:31 AM
I explain this question like this, fish have DNA the same as we do. This DNA tells the fish what it will look like, and how big it will grow, among other things. Now if you were to take a person at birth and put it into a box would the person only grow as big as the box allows? The answer is easy no, but it would end up with certain deformities, same as your fish will.

Ratlova30
04-28-2010, 12:48 PM
Thanks, I'll see what I can do. I was planning on upgrading his tank but it will have to wait for a little bit until I have more money.

KarlTh
04-29-2010, 10:18 AM
I explain this question like this, fish have DNA the same as we do. This DNA tells the fish what it will look like, and how big it will grow, among other things. Now if you were to take a person at birth and put it into a box would the person only grow as big as the box allows? The answer is easy no, but it would end up with certain deformities, same as your fish will.

Not quite as simple as that. Some animals' genomes do quite closely define their adult size; others don't, hence the monster carp several times the size of the average adult that fishermen occasionally catch.

It all depends what gives an evolutionary advantage. If there's an advantage to lower growth rates in less optimal conditions, then given the appropriate genetic code, that's what the organism will evolve to do.

jpappy789
04-29-2010, 2:03 PM
Not quite as simple as that. Some animals' genomes do quite closely define their adult size; others don't, hence the monster carp several times the size of the average adult that fishermen occasionally catch.

It all depends what gives an evolutionary advantage. If there's an advantage to lower growth rates in less optimal conditions, then given the appropriate genetic code, that's what the organism will evolve to do.

:iagree:

Nature and nurture (the environment) both play a role in how the genes are expressed.

cellodaisy
04-29-2010, 2:27 PM
It seems that the bottom line is a goldfish will not lead a long, healthy life in a ten gallon.


Thanks, I'll see what I can do. I was planning on upgrading his tank but it will have to wait for a little bit until I have more money.

Thank you for doing the right thing. Hopefully, you will be rewarded by having a healthy, beautiful fish for many years to come. :)