Does fish growth get stunted in an aquarium?

[Sordfish]

I was at my lfs, which is run by very knowledgeable staff. We were discussing which tangs can go into what size aquariums. At one point they mentioned that fish typically do not get as large in an aquarium. For example, if you put a baby yellow tang (think of those captive bred 1” babies that come translucent) in a 100 gallon tank, it is unlikely to grow beyond 5 inches - far smaller than the wild caught adults which get to be 8”.

I researched this but couldn’t find much beyond anecdotes - especially around goldfish. Has anyone come across any studies on this, either way? Just curious.

 

[EeyoreIsMySpiritAnimal]

This is a confusing topic, especially when dealing with marine life. I have no studies to cite, just knowledge I've acquired while researching various topics during my reefing journey.

In short, no. Do not buy a fish that you don't plan on keeping in an appropriately sized tank. (Buying a young fish with the plan to move it to a larger tank as it grows is fine.) A fish's size is only one factor; its habits are equally important. For example, a marine Betta gets as large as some tangs but is a more sedentary fish. Many other fish need lots of (horizontal) swimming room. Tangs in particular seem to "zoom" around the tank, and they need more space. So a 3-4" bristletooth tang might need a much larger tank than a 6-8" betta.
Some fish are more territorial (like clowns) and can be suitable in smaller tanks than fish that utilize the whole tank. I have clowns that are larger than my wrasse, but while I would be comfortable putting the clowns in a 30 gallon, the wrasse needs a 55+ gallon (standard size) tank. Again, some of it is the dimensions of the tank... standard 75 and 90 gallon tanks are both 48" long x 18" wide, but the 90 is taller; this difference is negligible when it comes to fish needs. But the difference between a 120 (48" long) and 125 (72" long) is much bigger, despite the fact that there only a 5 gallon difference.

 

[Fishnut]

FWIW Years ago I was into raising koi from eggs. I was told that daily massive water changes were the answer to fast growth. This is needed to eliminate the concentration fish hormones in the water which will, if left, slow and even stunt their growth. Is this the reason most fish never achieve full size in our aquariums?

 

[Sordfish]

FWIW Years ago I was into raising koi from eggs. I was told that daily massive water changes were the answer to fast growth. This is needed to eliminate the concentration fish hormones in the water which will, if left, slow and even stunt their growth. Is this the reason most fish never achieve full size in our aquariums?

Thanks. This is the kind of info I was hoping to find out. I am curious whether there is any concrete evidence that a fish raised in a tank will not grow to its full potential size and why that may be. Also curious if this has any health implications for the fish itself.

 

[davidcalgary29]

FWIW Years ago I was into raising koi from eggs. I was told that daily massive water changes were the answer to fast growth. This is needed to eliminate the concentration fish hormones in the water which will, if left, slow and even stunt their growth. Is this the reason most fish never achieve full size in our aquariums?

I was told the exact same thing by a veteran worker at a NLFS (I'm sorry, but a ten hour round trip is not "local"), and without evidence. I chalked it up as another apocryphal aquarium-trade story. Perhaps there's some truth to this in fish farms, where hundreds of specimens are kept in a single tank, but most of us keep only single specimens or a mated pair-- how could intraspecies competition become so intense in those conditions that it could lead to hormone saturation with a demonstrable physiological impact?

I think that wild fish are larger than aquarium specimens because most people can't keep their fish alive longer than a year or two, and the fact is that many fish can live for decades, and may not have terminal growth stages, and are therefore larger than what you'll likely find in home aquaria. It's going to be a long time before we (and I'm talking in generalities, and not @Paul B specifics) get to the stage where we can match life expectancies in the aquarium to what you'd find in a healthy ocean environment.

 

[sczlars]

I think it must be.. reading on Bob Fenner's wetwebmedia site, there is a lot of mention of "grows to x inches in the wild, much less in the aquarium".

 

[Dan_P]

I was at my lfs, which is run by very knowledgeable staff. We were discussing which tangs can go into what size aquariums. At one point they mentioned that fish typically do not get as large in an aquarium. For example, if you put a baby yellow tang (think of those captive bred 1” babies that come translucent) in a 100 gallon tank, it is unlikely to grow beyond 5 inches - far smaller than the wild caught adults which get to be 8”.

I researched this but couldn’t find much beyond anecdotes - especially around goldfish. Has anyone come across any studies on this, either way? Just curious.

Try searching this term “do aquarium fish grow big”. I think you will find that they can but many die young (probably very common) and those that live are not provided with adequate conditions.

 

[ISpeakForTheSeas]

There's some truth to the hormones/chemicals regulating growth in our aquariums (goldfish somatostatins are particularly well studied with this - see the quote and link below), but I'd guess that's not the whole picture. I'd assume things like stress, water quality issues, poor diet, and possibly even things like disease would all impact the growth of fish in aquaria.

Given that different organisms produce different chemicals and that different organisms respond differently to different chemicals, I don't know how much of a role hormone secretions actually play for any given fish in an aquarium, but I would guess that - in most cases - the role of hormones is probably pretty small compared to the roles of diet and keeping conditions.

It’s true for some fish (goldfish, which can actually get quite large, for example, produce growth inhibiting hormones - thought to be a way of trying to reduce competition between itself and other goldfish - so in a tiny tank, it will have stunted growth as a result of the hormone it produces), but for other fish the stunted growth (if it happens) is likely a result of a combination of things, namely stress, bad water quality, and poor diet.

The Role of Somatostatins in the Regulation of Growth in Fish - Fish Physiology and Biochemistry

Somatostatins (SS) are a structurally diverse family of peptide hormones that affect various aspects of growth, development and metabolism in vertebrates. Fish have proved to be useful models for understanding the role(s) of SS in the regulation of growth. Organismal growth is inhibited by SS...

link.springer.com

 

[Sordfish]

There's some truth to the hormones/chemicals regulating growth in our aquariums (goldfish somatostatins are particularly well studied with this - see the quote and link below), but I'd guess that's not the whole picture. I'd assume things like stress, water quality issues, poor diet, and possibly even things like disease would all impact the growth of fish in aquaria.

Given that different organisms produce different chemicals and that different organisms respond differently to different chemicals, I don't know how much of a role hormone secretions actually play for any given fish in an aquarium, but I would guess that - in most cases - the role of hormones is probably pretty small compared to the roles of diet and keeping conditions.

The Role of Somatostatins in the Regulation of Growth in Fish - Fish Physiology and Biochemistry

Somatostatins (SS) are a structurally diverse family of peptide hormones that affect various aspects of growth, development and metabolism in vertebrates. Fish have proved to be useful models for understanding the role(s) of SS in the regulation of growth. Organismal growth is inhibited by SS...

link.springer.com

Thanks for the link.

I can certainly believe that there are some deficiencies in aquarium conditions- this is what motivated me to ask the question in the first place. I would love to figure out what is missing - size, chemistry, something else? - and fix it. Also, are some fish more susceptible than others? Finally it raises the question as to whether fish in aquariums are doomed to an unhealthy and stressed life compared to their wild relatives. The above answers seem to suggest this is the case. Which of course would be very troubling. Alternatively, may be it is simple interactions of some harmless chemicals and has no bearing on the health and stress of the fish. Unfortunately it seems like there are few scientific studies that can provide answers.

 

[bobnicaragua]

Fish absolutely grow larger in bigger aquariums. I’ve been keeping salt water tanks since the mid 90’s and this has always been my experience.

If you put a one inch regal tang in a 29 gallon and a one inch regal tang in a 300 gallon, the tang in the 300 gallon will grow much bigger.

I had this little regal tang in my 29 gal for years back in the day. He never really grew much at all.

 

[Sordfish]

Fish absolutely grow larger in bigger aquariums. I’ve been keeping salt water tanks since the mid 90’s and this has always been my experience.

If you put a one inch Regal tang in a 29 gallon and a one inch Regal tang in a 300 gallon, the tang in the 300 gallon will grow much bigger.

This is good to know. Anyone else experienced this?

Also, did you ever transfer a fish that had stopped growing in a smaller tank to a larger tank and observe it to start growing again ?

 

[o2manyfish]

Fish grow for the space they have (usually). The best example I can give, from 100% personal experience, was a 1.5" yellow tang in my Dad's 40g reef tank. It went in at 1.5" and 14 years later when we broke the tank down it was transferred to one of my tanks and was 1.5". It was yellow, It was healthy, It had no HLLE and it didn't grow. When it went into a 180g frag tank it started growing again.

In my own tanks I have seen several fish do similar things. I have yellow and purple tangs that i have had for over 10 years. They are about 3.5"-4" in size. They are medium to med large, but are not at all large tangs. Mine have been in a 400g for at least 8 of those years, a 560g for almost 2 years and now a 750g.

In the 400g and then the 560g I had a pair of 6.5" blue tangs. I have seen blue tangs in public aquariums get over 14" long. But at 9 years they didn't pass 6.5". They had no HLLE and looked great (which the giant ones never do).

We had an Atlantic Blue tang we inherited from someone with a 90g tank who had it for 2 years and it had grown to about 2.5". It went into a 150g frag tank (only 10" depth). It was out there for about 18 months and barely grew. We moved that 2.5" tang into the 400g. In 3 months it tripled in size.

I've had the same experience with angels. I have kept a trio of Venustus in a 400g for 5.5 years. They were old enough to spawn but never got to the same size as some of the adults that come in from the wild.

I had a pair of orange belly regal angels. One started at 4.5" and the other at 3.5" - In 8 years neither fish probably increased in size by more than an inch.

I've dove with Naso tangs that are over 14" long. But in a 300g fish only after 6.5 years they never got past 8-10 inches.

Now there are some fish that don't follow these rules - Unicorn Tangs, Vlamingis - These guys will get really big in smaller sized tangs. They may not reach to 16-20" they get in really big tanks but they will definitely outgrow a comfortable size in a tank.

And the only fish I have kept that actually outgrew the physical tank were Queensland Groupers. I raised about 6 in highschool when I worked at a LFS. They outgrew 600g tanks - Where they would just sit (couldn't turn around). We would dump gold fish in by the hundred at one end of the tank and they would just vaccum them out of the water column. We got them up to about 6-7' long in 10' foot tanks. Before I left for college I made arrangements for them to goto Sea World in San Diego. 15 years later when I was visiting I inquired and most of the fish were still alive. They were almost the size of a VW Bus, and they had been transferred to multiple Sea Worlds, but they were still alive and growing.

Dave B

 

[Tritie]

I have koi ponds. Fry that are pulled out of the pond and raised in troughs so Mom and Dad don't eat them grow much slower than those that stay in the pond and manage to evade their hungry parents to grow up. I'm sure this also happens in the aquarium. I don't think that keeping a fish that grows large in a small tank is healthy for the fish. Stunted growth just means unhealthy or unhappy, at least to me.

 

[Seansea]

Yes i had a sailfin tang i got at 2 inches and at 7 years old he was 6" much less than the 10" ones i see in public displays. He was in a 150 and fed alot. He looked good. Fat and healthy just not big. As far as stressed they are better offin a well kept tank then in wild where they are eel or octupus food.

 

[ISpeakForTheSeas]

Thanks for the link.

I can certainly believe that there are some deficiencies in aquarium conditions- this is what motivated me to ask the question in the first place. I would love to figure out what is missing - size, chemistry, something else? - and fix it. Also, are some fish more susceptible than others? Finally it raises the question as to whether fish in aquariums are doomed to an unhealthy and stressed life compared to their wild relatives. The above answers seem to suggest this is the case. Which of course would be very troubling. Alternatively, may be it is simple interactions of some harmless chemicals and has no bearing on the health and stress of the fish. Unfortunately it seems like there are few scientific studies that can provide answers.

Yeah, as mentioned this is a really complicated topic because there are so many variables that go into it, so studying it in such a way as to have the findings be useful/meaningful for mutliple species would be incredibly time consuming (and there would likely be numerous potentially confounding variables for any mixed-species setups like the typical reef tank).

*For an example of a confounding variable, two different fish species might not show any stunted growth when kept by themselves, but then show stunted growth when kept together. In a situation like that, it could be a chemical put out by the other species inhibits the other’s growth, it could be caused by an interaction between chemicals put out by the two species, it could be a stress response, a response to aggression, a response to food competition, an attempt to appear less threatening, etc. (On the other side of this example, two fish species may show stunted growth when kept separately, but not together - this is, again, a whole can of confounding variable worms.)

With regards to fish in aquariums being “doomed to an unhealthy and stressed life,” I wouldn’t necessarily make that assumption. Just because a fish doesn’t grow to its maximum wild size doesn’t mean it’s unhappy (or even stressed at all). While that assumption is (to my knowledge) entirely possible, there are also a number of different possible explanations for the difference in growth (including, in addition to the possibilities listed above - though arguably unlikely - that the fish grow bigger in bigger tanks because they feel they need to in order to survive or increase their odds of survival; in other words, it’s possible- albeit unlikely- that they grow bigger in response to specific stressors::::similarly, the fish might stay small in smaller tanks because of some advantages it provides - such as requiring less food, as food would [at least theoretically in the fish’s mind] be less abundant because of the small available space for food to grow/hide).

Regardless though, I’d honestly assume the general health and happiness of the fish probably depends less on tank size (though I certainly believe it plays an extremely important role) and more on the care given them by the aquarist. A proper size of tank and proper care would likely provide a good quality, safe, stress-free, happy life for a fish. As was mentioned above, however, many people can’t keep their fish alive for a decent length of time (and fish that die young were probably pretty stressed).

Personally - disease aside - I’d guess a lot of premature fish deaths are largely because of improper diet (speaking candidly here, the more I learn about pet nutrition and pet food - and not just with fish - the more I realize that most pet foods, while possibly good enough to keep a pet alive for a while, are not good enough to keep a pet healthy/in peak physical condition long-term) and improper care (be it through poor water quality, bad tankmates, improper habitat, etc.). When you have proper care and proper diet, the fish live for long times (in some/many cases matching or exceeding their wild lifespans) and are happy enough to reproduce readily and exhibit their natural, wild behaviors. So, personally, I’d guess those fish are quite happy and content with their lives.

 

[Malcontent]

There's some truth to the hormones/chemicals regulating growth in our aquariums (goldfish somatostatins are particularly well studied with this - see the quote and link below), but I'd guess that's not the whole picture. I'd assume things like stress, water quality issues, poor diet, and possibly even things like disease would all impact the growth of fish in aquaria.

Given that different organisms produce different chemicals and that different organisms respond differently to different chemicals, I don't know how much of a role hormone secretions actually play for any given fish in an aquarium, but I would guess that - in most cases - the role of hormones is probably pretty small compared to the roles of diet and keeping conditions.

The Role of Somatostatins in the Regulation of Growth in Fish - Fish Physiology and Biochemistry

Somatostatins (SS) are a structurally diverse family of peptide hormones that affect various aspects of growth, development and metabolism in vertebrates. Fish have proved to be useful models for understanding the role(s) of SS in the regulation of growth. Organismal growth is inhibited by SS...

link.springer.com

Somatostatins aren't released into the environment. They are hormones which are released into the bloodstream. They can't affect other organisms.

Maybe you're thinking about pheromones (which somatostatins are not).

 

[AydenLincoln]

I’d argue that they adapt to their environment and given the best conditions they can live long and happy lives in captivity. But of course our tanks aren’t the ocean and will never be the ocean so they will behave, grow, and adapt differently.

 

[ErikVR]

This is absolutely true. BUT, they won’t live a long healthy life that way. Their growth gets stunned, including their organs. You might end up with a smaller fish but also a compromised fish.

 

[ISpeakForTheSeas]

Somatostatins aren't released into the environment. They are hormones which are released into the bloodstream. They can't affect other organisms.

Maybe you're thinking about pheromones (which somatostatins are not).

Ah, I didn’t phrase this very well there - sorry. You’re correct that hormones, Somatostatins included, are not generally released into the environment (exceptions given for those that come out in urine and such) - I was more just trying address that they are chemicals that do impact fish growth based in part on the size of the tank the fish is in. Looking over the answers above mine again, though, I can definitely see how that wouldn’t have come across that way.

That said, my second paragraph there definitely would have been better with “pheromones/hormones” being used rather than just “hormones.”

(Now I’m quite curious though if fish put out meaningful levels of hormones in their urine.)

 

[Timfish]

FWIW, average lenght of Yellow Tangs is 5 1/2" (14 cm). They also continue to grow throughout their lifespan (~35-40 years) so it seems like detreming max growth and size of captive raised fish that have only been available for a couple years doesn't seem realistic.