Do fish really stop growing if kept in a small tank?

[snoopy65]

I agree with JM. They appear to have stopped growing but they continue to grow all of their internal organs and eventually, because their body isn't big enough to hold all of the organs where they can function properly, they die of organ failure or disease well before they should or would have if kept properly.

 

[KarlTh]

I see this "internal organs keep growing" thing has been repeated again, but, as I suggested a page or two ago, still no-one's presented any evidence for it. I personally think it very unlikely and would like to see supporting evidence.

My suspicion is that it's a fishkeeping myth. Stunting is stunting; the whole fish is stunted. It's unhealthy, but I just don't buy this "internal organs keep growing" thing, not without some supporting evidence for it.

 

[jpappy789]

Of all the factors that lead to stunting in fish, I'd have to say that tank size is probably the least important determinant. Given ideal feeding regimen and flow through water changes, a fish will continue to grow to the point where it is no longer able to move within the confines of the aquarium. Studies have been done with channel catfish that do bear this out entirely. The issue becomes the feasibility of providing ideal conditions within the limited confines of an improperly sized aquarium. Suffice to say, the actual size of the tank is not the important part, rather the speed at which metabolic waste and hormones accumulate when there is not sufficient amounts of water moving through the aquarium. I voted no, because at the end of the day, its not the size of the tank, but rather the incompetence of the aquarist that leads to stunting.

I agree.

But the poll asks if tank size restricts growth, not if its the only factor.

Based on that I voted "yes" but there is definitely more to stunting than just tank size.

 

[bitbot]

I'm not convinced by the "internal organs continue to grow" stuff; the various body parts all respond to the same growth hormones AFAIK. Are there any papers supporting this, or is it just something that keeps getting repeated? Fish do indeed stunt, and it's not good for them, but I don't know that this internal organ stuff is the reason.

I'm not sure about that either.

I would stick with poor water conditons affecting their health. Maybe it makes them more prone to swim bladder type problems and that has given rise to the 'internal organs' thing?

Ian

Thanks for making this point, as I see this idea repeated over and over, but have never seen any evidence for it.

I would condemn keeping fish in too-small tanks, but I also condemn spreading misinformation, if that's what it is, even if it's well-meaning.

 

[santiago]

Fish never stop growing throughout their entire life until they die.

 

[Rbishop]

Fish never stop growing throughout their entire life until they die.

Please show some references for documentation..thanks....would love to read some proof of that...

 

[KarlTh]

Fish never stop growing throughout their entire life until they die.

My 2" Columbian tetras which have been that length for a year would beg to differ.

 

[12 Volt Man]

I see this "internal organs keep growing" thing has been repeated again, but, as I suggested a page or two ago, still no-one's presented any evidence for it. I personally think it very unlikely and would like to see supporting evidence.

My suspicion is that it's a fishkeeping myth. Stunting is stunting; the whole fish is stunted. It's unhealthy, but I just don't buy this "internal organs keep growing" thing, not without some supporting evidence for it.

agreed.

I have had quite a few fish over the years that lived to be 10+ years old, but never reached full adult size.

they displayed all the signs of being perfectly healthy too. although they began to show their age near the end (eg. silver dollars lose some of their lustre, clown loaches not as bright etc)

a lot of these particular fish I sold when I moved, so hopefully they are still alive to this day..

 

[12 Volt Man]

for the purposes of this thread, its worth noting a pair of lemon finned barbs I used to have, that reached 18" in length each in only a 90 gallon tank.

they were pretty cramped, but obtained this size because of massive water changes (weekly) and lots of food.

in a small tank, you generally can't feed as much and keep the water quality as clean as you can in a larger tank, so the fish do not get as much food and stay smaller as a result.

the hormone stuff as far as I can tell only seems to affect certain fish eg discus.

my barbs didn't care about hormones LOL

thats really what fish growth is all about:

lots of food + clean water = growth.

this is easier in a larger tank, so fish grow bigger

is more difficult in a smaller tank so they don't grow as big.

it only becomes a problem in extreme conditions (eg a 20" fish in a 30" tank etc) but in reality, your never going to get that situation because your fish will probably die from water quality related problems long before this..

 

[Signus]

The hormones are a myth.

Nitrogenous wastes, however, do impact fish health immensely. A fish given very small quarters will be stunted in TL (Total Length) due to physical injury and outgrowing the capacity of the filtration system.

You can also note that fish do not follow determinate growth like mammals, but will gain less total length over the years and focus on body depth. (Like determinate growth animals like humans.). This pattern follows a repeating sigmoid curve in decreasing rate.

Factors that affect fish length are:

Nutrition (More ideal nutrition early on supports longer TL)
Pollution (Water qualities)
Competition
and Predation

Rbishop, you would find a fisheries course at your state's university quite helpful.

"Bond's Biology of Fishes" By Michael Barton 2007 is an excellent read and useful in this knowledge.