Tank size does affect growth rates

[Jeff CC]

After many years of witnessing fish fail to come close to their max. size when kept in small to mid-sized tanks, including a Jack Dempsey that lived 14 years but never reached 5" despite being well-fed, I have concluded that fish, fresh and salt, do grow only to the size of their space.
To further test this idea, I kept 3 Clown fish in different sized tanks for 2+ years and witnessed the fish that were kept in the larger tanks grow to a larger size than their counterparts in smaller tanks. Anecdota evidencel, yes and I know many things affect growth rates... but evidence nonetheless.
If anyone out there has had a large fish grow close to full-size in a relatively small space, that would be of interest.

 

[Anonymous]

It's not necessarily the tank size that's affecting their growth rate. Water conditions, feeding, tankmates, etc. could all be different in the tanks and affect their growth.

Did you have the same exact filtration capacity, total water volume, etc. in every tank? If you were to do this scientifically, have a clown in a 20 with an 80 gallon sump, a clown in a 50 with a 50 gallon sump, and a clown in a 80 with a 20 gallon sump. Feed the exact same to each, have the exact same total lbs. LR, etc. Better yet, just link all the tanks together so they're all receiving the exact same water conditions.

Undoubtedly, fish will do best in the largest possible tank. I just don't think they grow to fit their tank size. I think a lot of former nurse shark owners will agree with me on this one.

Welcome to RDO!
Matt

 

[Anonymous]

This has been proven incorrect many times

 

[Anonymous]

I had a fish that growed biggest than my housed could handle without calling in the military. Ok..... ok.... calm down.I am just tryin to make a point here.

 

[Anonymous]

Not having any experience with this myself, I would think that it depends on the type of fish. Nurse sharks may grow in a cramped tank, but clownfish may be adapted to slow down growth in crowded conditions in the wild, a small anemone with too many fish for example.

There are several freshwater fish, turtles, and frogs that will slow down growth in small tanks...this is proven, but there are several others that will not slow down in small tanks.

Other stresses were mentioned, like water quality, as a factor in slow growth. Because having too small a tank stresses a marine fish, they may simply stay smaller because they are not in ideal conditions, rather than just to fit their tank size.

 

[Anonymous]

That's the reason why they stay small. It really doesn't have anything to do with tank size ALONE. All vertebrates (and some corals!) have determinate growth patterns--they sort of have a predetermined size range set at birth. You can certainly stunt their growth, but there's a limit to that.

 

[Jeff CC]

The total lack of science behind my conclusion is what has me hoping to find someone, anyone, who has actually experienced anything close to full growth rate in small to mid-sized tanks with either fresh or salt water fish. For instance, if a Yellow Tang kept in a 60 gal. tank grew to it's full max. size, that would prove something. Witnessing numerous specimens of many different species of fish, despite good care, fail to reach their reported potential size is mystifying. It is hard to imagine that the amount of space in their environment was inconsequential.

 

[Anonymous]

Jeff,
What exactly do you consider a small to mid-sized tank? Captive breeders keep mature clowns that have been raised their entire lives in captivity in pretty small tanks, around 40 gallons or so. These clowns get just as big as mature clowns in the wild. I have some clowns in a 180 gallon tank, and they don't really venture out of an area about the size of a 20 gallon tank.

Personally, I have a lionfish, Pterois volitans, that has reached the max size reported for the species in my aquarium. It started out around 8" or so and has grown to about 13" in a 275g tank.

 

[sammy stingray]

A former mod at another board wrote this reply several years ago on the subject. The guy was incredibly intelligent, and he brings up very interesting points. The truth contained, or lack of, can be decided for yourselves, but I found it interesting enough to still remember the post was buried years back. BTW his expertise was for disease and treatment. I thought I would dig it up and share it with you guys here...this was his reply in a thread pretty much about the exact same thing you guys are discussing here. Myself, I am not 100% either way because I simply don't have the research needed to not just guess, but here were his thoughts....



"GIH, or Growth Inhibitor Hormone, is constantly released into the water by most fish. It is a chemical used to compete against other fish in the wild through a complicated process not worth explaining.

In an aquarium, this stuff can build up, stunting the growth of the fishes in the tank.
HOWEVER, this is absolutely NOT desirable, since a lot of it has to build up to cause this stunting, and to get that amount, the tank has to be a cesspool suffering from great neglect.

Those who say that their fish only grew to the size of their tank should be ashamed of themselves, for their tanks have probably never seen a water change.
It's not just nitrates that accumulate, you know. There's all sorts of fun stuff like indoles, skatols, cresols, phenols, hormones, and much, much more. No matter how big a filter you have, or how deep your sand is, you must change water occasionally.

EXPERIMENT: Get a tank full of female guppies. Get a breeder net, and put males in it. Never change the water.
( As many of you know, females will turn to males without males present. This is why we include males in the net. )
Before very long, you will wind up with a big mess of ugly mutant fish of indeterminate gender. The hormones which would have been flushed away with water changes will instead build up in the water, causing changes. The females won't turn completely into males, for there will be too much accumulated female hormone ruining things.

Yes, if the water is dirty enough, growth will be stunted. However, growth will continue normally if the tank is kept under anything resembling normal conditions.

 

[sammy stingray]

BTW, he was a little harsh at times when he posted , but extremely intelligent and a wealth of info. Anyone here ever heard of "Growth Inhibitor Hormones"? This reply he made was the first and last time I had heard of them, and any links to info for further reading would be very appreciated.

 

[Apophis924]

Growth Inhibtor hormones?? Well if there is such a thing i would think they would be pretty useless in the wild due to the fact of the level they would be diluted to even in a small crowded pond or tide pool, the dilution factor is way beyond what we keep our aquairums at. even the 200 gal Plus sizes. Not to mention hormones being protien based would be removed by a skimmer in an enclosed system. Very few hormones can be absorbed in clinical concentrations from casual "contact" as in sharing the same tank with another animal. Most hormones are destoryed in the digetsive tract and those abosorbed thru the skin must have constant contact at extremely high concentrations to be effective. Take a fan tail gold fish and if you feed him a lot twice a day and keep his water "somewhat clean. That fish WILL grow huge be it in a ten gallon tank or a 50 gallon tank. I have yet to see tank size stunt the growth of one of these those things.

 

[sammy stingray]

So you think he was just blowing smoke? I don't know either way. I did read, many years ago, about deformed fish that were in too small of tanks. The article had pics as well. It's really hard in this hobby to sift through all the info when it conflicts on so many subjects. The hobby wasn't all that researched not too long ago, and it's still pretty new. This is always a very interesting subject IMO. Apophis924, lots of freshwater lakes are actually brown water due to the high organics. I actually think most of our reefs are much cleaner than many freshwater lakes. Obviously the seas are a different story, but perhaps he was more studied in Freshwater on the subject? I don't know that either, and I haven't spoken with him in years as far as I know. Some freshwater fishes live basically in tiny pools of water as rivers and small lakes dry up during droughts...perhaps this is when this would be needed? I'm not sure why a saltwater fish would need them, but perhaps? The fact they are protein based would go along with the fact he said the tank would basically have to be nasty in order for the hormones to have effect.

 

[Apophis924]

And for a tank to get that nasty for any hormones to have effect, the stunted growth would be more liley caused by toxins and the stress of living in a toxic enviroment. More energy would be used to maintian life than to grow and reproduce. Nature always takes the path of least resistance. Survive, Grow then reproduce. when your animals in captive enviroments start reproducing then you know you have met all of their requirements, life will only reporduce when the needs of survial and growth are first met. It would be a bilogical waste of energy and resources to produce growth inhibiting hormones. hormones cost a lot of biological enegry to manufacture. Size is genetic, yes to a degree enviroment will have an effect, an animal cannot reach its full potiental if it is not fed enough or it is using its energy to combat enviroment pressures. But I know of no reserach or animal that actively uses growth inhibiting hormones as a method of dealing with competition with other life in its enviroment. In a small finite space of a pond or even a puddle the hormone level would rise so fast that ALL the life in the pond would be affected. If you look at desert shrimp and frogs when the pond gets croweded they feed on eachother, a much more economical way of dealing with competiotion than limited the others growth by emission of inhibitory hormones. But then again who can be sure, I just havent seen any factual data besides a cut and paste on a website. Life always finds way.

 

[Anonymous]

I dunno, it smacks of allelopathy to me. I've heard of GIH, not applied to fishes in any way, but I have read of them briefly. I wouldn't be surprised if what he mentioned may be a very real issue for food fish farmers. (Mm... I just remembered that tilapia I had a few weeks ago.. MAN was it good! I'm hungry.)

I agree, SamSting (I am also glad you're participating every once in a while! ), this is an infinitely interesting subject. For instance, we know that high levels of several stress hormones present in human children can stunt not only their physical growth, but their psychological growth as well. This is borne out by research showing that severely abused children have marked physiological differences in their brains.

So, I ask it this way: why not fish? Just because we haven't seen much in the way of factual data doesn't mean it doesn't exist. The instances you bring up, Apophis, are good examples, but rather.. specific (the desert fishes and frogs) to their evolution. If you think about it, they can't utilize something like a GIH, or they'd stunt themselves out of existence.

Now, consider the wooly mammoth. Big, smelly, HUGE animal, right? Now, consider the fossil evidence of dwarf mammoths found on a small island off the coast of California (sorry, cannot for the life of me remember which island.. one of the Channel islands I think?). With many such isolated populations, they had to "grow down" rather quickly in the evolutionary timescale. Maybe (just maybe), there's some recessive/subordinate genetic response, in the form of hormonal response, that allows for this.

Hey, it's just a thought. I'm with Sammy, jury's still out (at least, until I have time to take a better look around).

 

[Anonymous]

A lot of things that are non-hormonal are attributed to hormones...like when my wife gets pissed off, I think its hormones, but then I realize that she just gets pissed off. :lol:

Some species may be predisposed to inhibit growth in crowded situations. Hormones may not be a factor at all. In order to survive, the fish slows growth, knowing that there is little space for him, and therefore less food. Being bigger requires more food and larger territory. An anemone can only support so many clownfish in the wild for example. A small anemone would not be enough for a few very large clownfish, but may be fine for the same number of mid-sized clowns. Evolution may program these fish to slow growth in order to be able to keep their home and not have to move on to a larger one.

This is only a thought, not a theory, so don't go tearing it up. :wink:

I get this from turtles, the little ones you buy at the petshop with the red stripe on the head. They will stay smaller in smaller tanks because they do this in the wild. In small ponds that can't support large turtles, the turtles grow slowly or else they wil get too big and starve. They can still reproduce and they put energy into that, but growth would actually be a detriment and make reproduction harder because there isn't enough food or space for the larger turtles.

 

[Quigonsean]

I dunno about this stuff, but I did read in Aquarium USA or Tropical Fish Hobbyest. That when breeding fish (THese where all FW and where Live Bearers, Convict Chiclids, Betta's and Danios) that you should do freaquent water changes on the fry rearing tank because the fry release a hormone that will stunt growth if water changes are not done. Now this was only speaking of fry in their early stages and it was FW. But in that respect I've heard of Gowth Inhibiters.

Sean

 

[Anonymous]

I've never heard of such a thing. What I can tell you is this: In both intensive (recirculating) and extensive (flow-through) systems of white sturgeon (Acipenser transmontanus) aquaculture, there's virtually no difference in growth rates. The methods for filtering the intensive systems are pretty much bio-balls and sand filters, there's no type of chemical filtration to remove hormones. The fish are stocked VERY heavily, much more heavily than any aquarium. You can stick your hand in the water anywhere and you'll probably touch a fish. Not only do these fish grow much faster than wild fish, they reach sexual maturity at about half the age of wild fish.

The same is true for catfish. Most of the ponds in the south where they're raised are non-circulating--it's just stagnant water. Every now and then they will areate the water on very hot and non-windy days, but there is virtually no filtration at all other than what the freshwater algae is soaking up. Likewise, they feed these fish a lot and they grow like crazy.

Growth Inhibtor hormones?? Well if there is such a thing i would think they would be pretty useless in the wild due to the fact of the level they would be diluted to even in a small crowded pond or tide pool, the dilution factor is way beyond what we keep our aquairums at. even the 200 gal Plus sizes.

I'm not so sure about the dilution effect in the wild. Sturgeon certainly do release hormones into the water to induce spawning in those of the opposite sex. It's also done in fast moving, clean river water. Sturgeon won't lay eggs on silty or sandy substrates, only hard, clean ones. If they can do it, I don't see why other hormones couldn't have effects in small amounts.

 

[Anonymous]

Manny, think about it, without hormones, what, exactly, would trigger these responses? There has to be something that does this, the animal can't look at its situation and consciously "know" that it needs to do this or that, so when you say "genetically programmed", I think it means "genetically programmed to respond in 'such and thus' manner to 'such and thus' triggers". There has to be a means of getting the message across to the body, and that is exactly what hormones do.

 

[Anonymous]

the physical size of the 'room' one keeps any animal in never has anything to do with the size that animal will grow to-thinking otherwise is ridiculous, imo.

kinda like saying if you were placed in a small room as a child-you'ld be a midget-that supposition is just as ridiculous for zebras, whales, birds, or fish

i've seen 3 oscars get to about 10" growing up together, in a 30 gal tank

i've seen one oscar get to about the same size in a 20

i've raised tilapia in closed systems, where the amount of water, by volume, in the system, was only slightly larger than the volume the fish occupied-imagine a concrete cube containing what appears to be an almost solid mass of fish

the only thing that ever affected the growth rate of any fish in a captive setting is deteriorating water quality conditions, whether the result be an elevated level of antigrowth hormones secreted by the fish, or an elevated waste level

an animal's size potential is preprogrammed via its genetics-the realization is not affected by the 'roaming range' that animal has, but rather by it's ability to consume the right amount of energy/elements required for growth, and a clean environment

just my $0.02

 

[Anonymous]

i'm also willing to bet that growth, like so many other physiological processes, are indeed regulated by some hormone or other-most hormones, iirc work by negative feedback loops-this seems to reflect what happens to animals in overpopulation situations :wink: