# Fish don't grow to size of tank...



## Imbrium (Feb 7, 2005)

Ok, I know fish don't stop growing just because they're in a small tank. I know everyone says that their internal organs keep growing, and they deform, and die horrible deaths. I'm not debating any of these things. I'm just looking for a source. Where did this information come from? Are there scientific articles discussing this?


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## Beerleader (May 31, 2005)

Not sure either but I'll tell ya my arrowana is a prime example, I had him in a 10 gallon when he was 3 inches then moved him to 55 because he doubled to 6 inches in 3 weeks, so I assume he's gonna keep growing at this pace no matter what tank he's in hehe


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## fishfreaks (Jan 19, 2005)

yeah ive never seen any source proving it.


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## TheOldSalt (Jan 28, 2005)

Well, I don't know about the deformed organs and such, but here's the deal:

If you don't keep the water changed, GIH will build up in the tank and stunt the growth of the fish. This is a bad thing. If you DO keep the water clean, the fish will grow normally and then possibly wind up very cramped and possibly even deformed in the case of very large species, but otherwise probably not. Either way, you just can't win.

A source? 
Hmmm... I can't think of any, but it's one of those things everybody just knows.


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## shev (Jan 18, 2005)

yeah, its common knowledge.


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## Damon (Jan 18, 2005)

http://www.bemidjistate.edu/dsiems/research.htm#stunting


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## TheOldSalt (Jan 28, 2005)

In case you were wondering just why something like GIH ( Growth Inhibiting Hormone ) would even exist, the link that Simpte provided above has a lot to do with that, even though it isn't very obvious. As a survival strategy, populations faced with severely limited resources will sometimes become reduced in size in an effort to reduce the resource needs of the individuals. Take a look at the Keys Deer, for example, which started out as a splinter population of ordinary Whitetails but they shrunk in order to better get by on the limited range and resources offered by their new habitat. Fish measure the size of their pond in relation to the size of their population by the concentration level of GIH in the water. It's kind of like a chemical radar in a way, you might say. When the GIH level gets high, it indicates to the fish that the population level of the species is too high, causing the fish to retard their growth until things improve.


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## Mr Aquarium (Jan 18, 2005)

> As a survival strategy, populations faced with severely limited resources will sometimes become reduced in size


Yup, this is true for any living creature or person,
you don;t see and people from Japan that are over weight do ya


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## sbsociety (May 1, 2005)

Mr Aquarium said:


> Yup, this is true for any living creature or person,
> you don;t see and people from Japan that are over weight do ya


Ummm... I think that's cause they don't have a MacDonald's on every corner.  lol. Naw, really though, it's the different food. Not adaption. 

And yes, different species adapt to their environment as a form of survival. "Survival of the fittest" as I'm sure you've all heard before. Anthropology theory... Don't feel like explaining all that. lol (Look up Charles Darwin's theory)

I don't know if that's really considered similar to what you guys are talking about though... It's not an actual chemical with an inhibitor, goes more into physical adaptation.


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## euRasian32 (May 19, 2005)

Mr Aquarium said:


> Yup, this is true for any living creature or person,
> you don;t see and people from Japan that are over weight do ya


:raises hand:

so sumo wrestlers are just big boned?


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## shev (Jan 18, 2005)

lol

The stereotype of japanese people being small is because when the population increased, meat became scarce and their diet mostly consisted of vegetables and rice. but nowadays, they arent all short because their diet has changed so much.


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## Imbrium (Feb 7, 2005)

Yeah, I know it's just common knowledge. I was just hoping somebody had some background info for it. I know about GIH, and I wasn't really concerned with the gradual shrinking of a group over generations. I was looking more for info on a fish that could potentially grow to full size.


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## TheOldSalt (Jan 28, 2005)

Hmmm... well, fishfarms and discus growers make lots of very large and frequent water changes in order to keep growth optimized, if that's anything you can use. If you're trying to get a fullsized Arapaimia in a 3000 gallon tank or somesuch, then I suppose it's theoretically doable.


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## Fishfirst (Jan 24, 2005)

quote: Ummm... I think that's cause they don't have a MacDonald's on every corner. lol. Naw, really though, it's the different food. Not adaption. 

And yes, different species adapt to their environment as a form of survival. "Survival of the fittest" as I'm sure you've all heard before. Anthropology theory... Don't feel like explaining all that. lol (Look up Charles Darwin's theory)

I don't know if that's really considered similar to what you guys are talking about though... It's not an actual chemical with an inhibitor, goes more into physical adaptation.


Adaption is directly related to the environment, the food they eat is adapted because there isn't a lot of meat eaten by japanese people due to thier limited resources. Way back when, when foods such as meat were not able to be imported or baught caused a general widespread shortage. This shortage created a ressesive trait in the genetic code (being smaller in size/shorter) to be more favorable over thousands of years. This genetic change is still present today, but the large gene isn't completely gone from this genetic code since so many genes control whether you are large or small, which is why you have the large sumo wrestlers still in the gene pool.

Same with the Inhibitor hormone, the hormone evolved to control a fishes population. In overpopulated areas, GIH is high which causes slower growth, slower maturity, and a greater chance for mortality, which lowers the population and prevents them from going over MSP (maximum sustainable population) for long period of time. Its very similar to what we are talking about... since it happens in the wild when populations are out of control, it will happen in the home aquarium too. GIH is the key to the whole stocking/enough room for the individual fish/frequent water changes debate.


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