Ye old stocking limit question!

Craig Manoukian · 02-09-2007, 02:14 AM

This has been reproduced from a link at MarineDepot www.marinedepot.com here in So. Cal. It identifies the basis for the 1" of mature fish per 5 gallons of water volume guideline that we acknowledge here on this site. Plan your bioload appropriately and remember that better filtration/water quality is better for your fish. Enjoy!

Inches to gallons, and creating a midget fish? The full explanation...

When asking about proper stocking rates for both fresh and salt water aquariums, the most often offered yet most misunderstood advice is the phrase "one inch of fish to a gallon of water" (or, in salt water circles, one inch of fish to three to five gallons of water). This mini-article will properly explain the basis behind the phrase and how it translates into deciding upon stocking rates for your aquarium (from a biological load and water quality perspective only - behavioral issues are not discussed but may have to come into play, such as territory requirements of the particular species). This is not scientifically exact, but it is a very good guideline/rate calculating system to use to ensure that the starting hobbyist won't crash their tank by stocking it with a load greater than the tank environment can easily handle and process.

Definition of an inch

This refers to a freshwater fish that at one inch long has the same body mass as a livebearer, like a molly, or a tetra, meaning a fish that is about 1/2 inch thick, and 1/2-3/4 inches tall. The saltwater equivalent would be a small damselfish, like the blue devil damsel, that is about 3/4" tall, and 1/2" (app) thick.

Meaning of a gallon

The gallon is the amount of water needed to sufficiently dilute the waste level the fish creates, to enable it to be comfortable, until the filtration can break the wastes down into less poisonous substances. So, a 1" long molly will need a gallon of water to dilute it's urine, CO2, and fecal matter to a level it can "deal with" until the wastes get carried to the filtering process (whatever that may be). A 1" damsel will need 3-5 gallons of water for the same "comfort level".

What does all this mean?

NOW, keep in mind the whole body mass issue mentioned above. If we take a different type of fresh water fish, like an Oscar, for example, we can see that the load factor, or biomass, per running inch, is not the same as a molly. The Oscar is both thicker and taller than the molly is, and represents a far higher load factor. (Think of how many mollies can fit into the space occupied by the Oscar's body - it will take at least 20-30 mollies, to equal the body mass of a 5" long Oscar, if they were fit next to and stacked upon one another like sardines). Every running inch of Oscar is at least twice as thick as a molly and quite a few times (15-20 times the height for an adult Oscar) taller. A 5" long Oscar would require a 20-30 gallon tank, ALL BY ITSELF, for proper comfort and life support-with filtration. A full grown Oscar can completely fill a 75-100 aquarium by itself, from a carrying capacity standpoint.

Metabolism also plays a role for the determination - a sedate fish will place less load factor on a system than an active fish will, per the same amount of biomass, as the more active fish needs to eat more, and will produce more waste, to support the same amount of actual biomass.

The same rules apply for a saltwater tank, though the ratios are a bit different, and the metabolism factor also needs to be considered. For example, a Tang requires far more space and swimming room than it's body mass alone would lead one to figure - they require very large amounts of oxygen, and release larger amounts of CO2, per unit of body mass, than a lionfish does, for example, and their behavior demands lots of swimming room.

Can a cube create a midget? (The "tank size affecting fish size" myth exposed and explained)

Many years ago, before the underlying concepts of waste management in closed systems and how they affect growth rates in fish were understood, people who kept aquaria didn't really understand the need for performing water changes. They also noticed that fish tended to stop growing at an earlier age in smaller tanks, than they did in larger tanks. This lead to the erroneous assumption that the physical size (dimensions) of the tank determined the physical size of the fish. Nothing could be further from the truth.

Here's why:

All animals will reach the size they grow to as a function of their genetic potential and their ability to take advantage of that potential. To illustrate, let's look at people - even siblings grow up to be different heights because the genes that determine growth rate and final size are different for everyone. As long as one receives proper nutrition and exercise, and is kept in good health, one will reach the maximum height that one's genes will allow for. Raising a child in a bathroom, will not turn them into a midget, as long as they get proper diet and perform calisthenics/exercise, have access to good fresh air and water to breathe and drink, (though they may go mental from boredom ;p ), and aren't subject to re-breathing their own CO2, or re-consuming their own waste. Also to illustrate, if you try to keep an elephant in a 6'x6' cube from birth, it will not become a cube shaped elephant measuring 6'x6' as an adult. You will end up with a busted cube. ;p

If an Oscar is kept in a 20 gallon tank, that is then plumbed/piped into a 1000 reservoir system, it will reach a foot long in spite of the physical size of the tank-since it's wastes are not building up in the system to the point of interfering biologically with it's growth potential. Alternatively, you can achieve the same result by performing daily water changes. One of the main waste products that fish produce is an anti-growth hormone, the function of which is most likely to ensure that the largest fish from a group of offspring, get a better survival chance than their slower growing siblings, to help increase the percentage of faster growing (and therefore better suited for survival) offspring in successive generations. This is often observed in closed systems.

When rearing fry:

Out of any group of fry, a small percentage will always start to grow faster than the rest of the group, and that smaller percentage will ALWAYS remain the largest. If the larger fry are then removed, another amount of fry will then "spurt" in growth, while the remainder does not, and so on. This is due to the presence of that anti-growth hormone. Again, water changes, or a corresponding increase of waste dilution ability due to an increase in water volume, will mitigate the effects and concentration of the levels of that hormone in the water.

The bottom line is that the physical dimensions of any aquarium have nothing to do with the end size of a fish, the management and water quality do.

saltwaterfarm · 02-09-2007, 02:38 AM

Great info Craig...

lcstorc · 02-09-2007, 08:38 AM

Great reading! Thanks!

goldenmean · 02-09-2007, 12:55 PM

Very interesting indeed!

Cougra · 02-09-2007, 01:51 PM

Quote:

Meaning of a gallon

The gallon is the amount of water needed to sufficiently dilute the waste level the fish creates, to enable it to be comfortable, until the filtration can break the wastes down into less poisonous substances. So, a 1" long molly will need a gallon of water to dilute it's urine, CO2, and fecal matter to a level it can "deal with" until the wastes get carried to the filtering process (whatever that may be). A 1" damsel will need 3-5 gallons of water for the same "comfort level".

Just to add a bit more to this explaination:

Fish skin is semi-porous and is affected by osmosis. Both saltwater and fresh water fish have an internal salinity (if this is the improper term I appologize, I'm not a biologist) that is different from their environment.

Fresh water fish have a higher internal salinity from their environment so their bodies are constantly bombarded with excess freshwater that tries to dilute their internal chemistry. To cope with this they drink very little water and produce a lot of very dilute urine to expel the excess water in their system.

Salt water fish on the other hand have a lower internal salinity so the water in their system is constantly being lost to the external environmentwhich could cause them to dehydrate. To cope with this constant loss of water, they drink a lot of water and produce very little and very concentrated urine.

boozeman · 02-09-2007, 04:41 PM

scientific term = osmotic regulation

cheeks69 · 02-09-2007, 06:22 PM

I did read this article and found it interesting.
The thing I find curious is if the smaller tank size will not stunt growth why is that I've never seen a fish that grew up in a captive environment grow as large as their wild counterparts ?

Quote:

anti-growth hormone

Boomer had mentioned this before in some older threads but again even in systems that maintain excellent water quality I have never seen this happen unless the fish was captured as an adult.

Craig Manoukian · 02-09-2007, 07:04 PM

Remember that a gallon of water is just that. Sand and live rock displace and reduce the gallonage calculated by tank dimensions. Net gallons is the parameter.

prow · 02-09-2007, 08:02 PM

i think its only an OK rule of thumb. just ok. more of factor is the fish and its behavior. follow those, of the full grown version of whatever fish, 9 out of 10 times you will be under the one inch per gallon number. i have always run into not enough room because of aggression and/or feeding needs. usually bio load does not become a factor. IME

extexan · 06-26-2007, 03:12 PM

My wife and daughter constantly ask me the age-old question: How many fish can we put in the tank? I have to bite my lip, and calmly say that it's not important how many fish we put into the tank, it's that we find specimens that get along with each other and have lots of room to live peacefully. I guess I'm not getting through to them...they still ask.

Craig Manoukian · 07-01-2007, 07:28 AM

Great husbandry all the way around extexan!

BoomerD · 07-01-2007, 11:18 AM

On WWM, Fenner recommends 5 gallons of water for each CUBIC inch of fish...not linear inch...THAT takes into account the mass of the animal much better than the 1"/5 gallons figure, because as we all know, one 6" fish will certainly create more waste and bio-load than six 1" fish will...thus, measuring the cubic inches of the fish...makes great sense...but of course, isn't nearly as easy to figure, and will reduce the number of pretties we can have in the tank...(which in reality, isn't a bad idea anyway)

Craig Manoukian · 07-01-2007, 11:31 AM

Just to let others know I play by the rules;

my next tank will be 45 gallons with a 30 gallon refugium and I'm planning a mated pair of Skunk Clowns and three or four Rainsford Gobies (which a very small thin fish) in the display. An Anemone for the clowns, an ornamental clam, and a pair of Harlequin Shrimp will round out livestock other than cleaning crew (nassaurius, turbo and trochus snails, scarlet hermits, fighting conches , and polecheates).

This is a minimum bioload for 75 gallons of water total volume.

ScubaDrew · 09-17-2007, 10:52 PM

Thanks for the info, its a little dissapointing that in a 92 gal corner I can fit so few fish.

Figure 92gal +20 gal sump and refuge - LR - sand = 90 gal. /5gal per inch = 18 inches.

My foxface has a max growth of 9inches. leaving me one other fish of similar size. This calculation seems way off from what most other people have listed in tanks of similar size.

I like the info, but it seems off compared to what most people practice.

GeeWizzItsMe · 09-17-2007, 11:04 PM

I agree with Scuba. It seems like the only person following this law is Melanie... (Great job!!) I have read in a few books that 1 inch of fully grown fish per gallon is all it takes (thats even without protein skimmer!) Maybe these are old books, but it just seems strange...

02-09-2007, 02:14 AM	#1 (permalink)
Craig Manoukian Regular Guy Moderator Join Date: Nov 2003 Location: Marina Del Ray, CA Posts: 18,179 View Gallery Karma Komment Add yours!	Ye old stocking limit question! This has been reproduced from a link at MarineDepot www.marinedepot.com here in So. Cal. It identifies the basis for the 1" of mature fish per 5 gallons of water volume guideline that we acknowledge here on this site. Plan your bioload appropriately and remember that better filtration/water quality is better for your fish. Enjoy! Inches to gallons, and creating a midget fish? The full explanation... When asking about proper stocking rates for both fresh and salt water aquariums, the most often offered yet most misunderstood advice is the phrase "one inch of fish to a gallon of water" (or, in salt water circles, one inch of fish to three to five gallons of water). This mini-article will properly explain the basis behind the phrase and how it translates into deciding upon stocking rates for your aquarium (from a biological load and water quality perspective only - behavioral issues are not discussed but may have to come into play, such as territory requirements of the particular species). This is not scientifically exact, but it is a very good guideline/rate calculating system to use to ensure that the starting hobbyist won't crash their tank by stocking it with a load greater than the tank environment can easily handle and process. Definition of an inch This refers to a freshwater fish that at one inch long has the same body mass as a livebearer, like a molly, or a tetra, meaning a fish that is about 1/2 inch thick, and 1/2-3/4 inches tall. The saltwater equivalent would be a small damselfish, like the blue devil damsel, that is about 3/4" tall, and 1/2" (app) thick. Meaning of a gallon The gallon is the amount of water needed to sufficiently dilute the waste level the fish creates, to enable it to be comfortable, until the filtration can break the wastes down into less poisonous substances. So, a 1" long molly will need a gallon of water to dilute it's urine, CO2, and fecal matter to a level it can "deal with" until the wastes get carried to the filtering process (whatever that may be). A 1" damsel will need 3-5 gallons of water for the same "comfort level". What does all this mean? NOW, keep in mind the whole body mass issue mentioned above. If we take a different type of fresh water fish, like an Oscar, for example, we can see that the load factor, or biomass, per running inch, is not the same as a molly. The Oscar is both thicker and taller than the molly is, and represents a far higher load factor. (Think of how many mollies can fit into the space occupied by the Oscar's body - it will take at least 20-30 mollies, to equal the body mass of a 5" long Oscar, if they were fit next to and stacked upon one another like sardines). Every running inch of Oscar is at least twice as thick as a molly and quite a few times (15-20 times the height for an adult Oscar) taller. A 5" long Oscar would require a 20-30 gallon tank, ALL BY ITSELF, for proper comfort and life support-with filtration. A full grown Oscar can completely fill a 75-100 aquarium by itself, from a carrying capacity standpoint. Metabolism also plays a role for the determination - a sedate fish will place less load factor on a system than an active fish will, per the same amount of biomass, as the more active fish needs to eat more, and will produce more waste, to support the same amount of actual biomass. The same rules apply for a saltwater tank, though the ratios are a bit different, and the metabolism factor also needs to be considered. For example, a Tang requires far more space and swimming room than it's body mass alone would lead one to figure - they require very large amounts of oxygen, and release larger amounts of CO2, per unit of body mass, than a lionfish does, for example, and their behavior demands lots of swimming room. Can a cube create a midget? (The "tank size affecting fish size" myth exposed and explained) Many years ago, before the underlying concepts of waste management in closed systems and how they affect growth rates in fish were understood, people who kept aquaria didn't really understand the need for performing water changes. They also noticed that fish tended to stop growing at an earlier age in smaller tanks, than they did in larger tanks. This lead to the erroneous assumption that the physical size (dimensions) of the tank determined the physical size of the fish. Nothing could be further from the truth. Here's why: All animals will reach the size they grow to as a function of their genetic potential and their ability to take advantage of that potential. To illustrate, let's look at people - even siblings grow up to be different heights because the genes that determine growth rate and final size are different for everyone. As long as one receives proper nutrition and exercise, and is kept in good health, one will reach the maximum height that one's genes will allow for. Raising a child in a bathroom, will not turn them into a midget, as long as they get proper diet and perform calisthenics/exercise, have access to good fresh air and water to breathe and drink, (though they may go mental from boredom ;p ), and aren't subject to re-breathing their own CO2, or re-consuming their own waste. Also to illustrate, if you try to keep an elephant in a 6'x6' cube from birth, it will not become a cube shaped elephant measuring 6'x6' as an adult. You will end up with a busted cube. ;p If an Oscar is kept in a 20 gallon tank, that is then plumbed/piped into a 1000 reservoir system, it will reach a foot long in spite of the physical size of the tank-since it's wastes are not building up in the system to the point of interfering biologically with it's growth potential. Alternatively, you can achieve the same result by performing daily water changes. One of the main waste products that fish produce is an anti-growth hormone, the function of which is most likely to ensure that the largest fish from a group of offspring, get a better survival chance than their slower growing siblings, to help increase the percentage of faster growing (and therefore better suited for survival) offspring in successive generations. This is often observed in closed systems. When rearing fry: Out of any group of fry, a small percentage will always start to grow faster than the rest of the group, and that smaller percentage will ALWAYS remain the largest. If the larger fry are then removed, another amount of fry will then "spurt" in growth, while the remainder does not, and so on. This is due to the presence of that anti-growth hormone. Again, water changes, or a corresponding increase of waste dilution ability due to an increase in water volume, will mitigate the effects and concentration of the levels of that hormone in the water. The bottom line is that the physical dimensions of any aquarium have nothing to do with the end size of a fish, the management and water quality do. __________________ Currently tankless. 20 Gallon mini reef with mated pair of Maroon Clowns given to Rougiem! 80 gallon reef given to Rougiem/Wooster HS.

02-09-2007, 02:38 AM	#2 (permalink)
saltwaterfarm Manta Ray Join Date: Oct 2006 Location: Maryland Posts: 3,222 View Gallery Karma Komment Add yours!	Re: Ye old stocking limit question! Great info Craig... __________________ Lisa 90 Gal AGA, DIY Sump/Fuge, Current Outer Orbit 250w MH's with T5's. AquaC Remora Pro Skimmer, RK2.[/font] Purple LTA, pair of Percula Clowns, Clams, Softies, Shrooms, Ricordea, Echinophyllia, Torch, Frogspawn, Blastos, Sponges, Acro, Wellso, the NEW Zoa Mountain, and some more stuff... 3 Gal Sexy Shrimp Pico. 29 Gal Oceanic BioCube, Current Sunpod 150w MH.

02-09-2007, 08:38 AM	#3 (permalink)
lcstorc Sunshine Reefer Join Date: Mar 2006 Location: Cocoa Fl Posts: 19,905 View Gallery Karma Komment Add yours!	Re: Ye old stocking limit question! Great reading! Thanks! __________________ Peace LYNN You can't change the past but you can change how you view it. A reef tank is like a racecar. The faster you go the harder you crash. Lynn and Franks saltwater adventure Lynn's 20g clown tank Lynn's 90g of sunshine Every 60 seconds you spend upset is a minute of happiness you'll never get back. In Loving Memory Of Z 01/22/07 - 08/19/08

02-09-2007, 12:55 PM	#4 (permalink)
goldenmean Beautiful Katamari Join Date: Apr 2006 Location: Chicago Posts: 4,183 View Gallery Karma Komment Add yours!	Re: Ye old stocking limit question! Very interesting indeed! __________________ A 55g link in the GoldenChain My 2nd-QT-Wrasse My Second Quarantine Tank 2 (+) Year Retrospective of a 12g Nano Jeff What You Think Upon Grows... Have a Smooth Day!

02-09-2007, 04:41 PM	#6 (permalink)
boozeman The CodFather ~ Join Date: Apr 2006 Location: new york Posts: 8,800 View Gallery Karma Komment Add yours!	Re: Ye old stocking limit question! scientific term = osmotic regulation __________________ ...and when I'm old and wise little things mean little to me like autumn winds they'll blow right through me and someday, in the mist of time when they ask you if you knew me remember that you were a friend of mine

02-09-2007, 07:04 PM	#8 (permalink)
Craig Manoukian Regular Guy Moderator Join Date: Nov 2003 Location: Marina Del Ray, CA Posts: 18,179 View Gallery Karma Komment Add yours!	Re: Ye old stocking limit question! Remember that a gallon of water is just that. Sand and live rock displace and reduce the gallonage calculated by tank dimensions. Net gallons is the parameter. __________________ Currently tankless. 20 Gallon mini reef with mated pair of Maroon Clowns given to Rougiem! 80 gallon reef given to Rougiem/Wooster HS.

02-09-2007, 08:02 PM	#9 (permalink)
prow Manta Ray Join Date: May 2005 Location: Redondo Beach, CA Posts: 3,936 View Gallery Karma Komment Add yours!	Re: Ye old stocking limit question! i think its only an OK rule of thumb. just ok. more of factor is the fish and its behavior. follow those, of the full grown version of whatever fish, 9 out of 10 times you will be under the one inch per gallon number. i have always run into not enough room because of aggression and/or feeding needs. usually bio load does not become a factor. IME

06-26-2007, 03:12 PM	#10 (permalink)
extexan Tunicate Join Date: Jun 2007 Posts: 24 View Gallery Karma Komment	Re: Ye old stocking limit question! My wife and daughter constantly ask me the age-old question: How many fish can we put in the tank? I have to bite my lip, and calmly say that it's not important how many fish we put into the tank, it's that we find specimens that get along with each other and have lots of room to live peacefully. I guess I'm not getting through to them...they still ask. __________________ Onward through the fog!

07-01-2007, 07:28 AM	#11 (permalink)
Craig Manoukian Regular Guy Moderator Join Date: Nov 2003 Location: Marina Del Ray, CA Posts: 18,179 View Gallery Karma Komment Add yours!	Re: Ye old stocking limit question! Great husbandry all the way around extexan! __________________ Currently tankless. 20 Gallon mini reef with mated pair of Maroon Clowns given to Rougiem! 80 gallon reef given to Rougiem/Wooster HS.

07-01-2007, 11:18 AM	#12 (permalink)
BoomerD Reef Shark Join Date: Nov 2003 Location: Northern California Posts: 5,637 View Gallery Karma Komment	Re: Ye old stocking limit question! On WWM, Fenner recommends 5 gallons of water for each CUBIC inch of fish...not linear inch...THAT takes into account the mass of the animal much better than the 1"/5 gallons figure, because as we all know, one 6" fish will certainly create more waste and bio-load than six 1" fish will...thus, measuring the cubic inches of the fish...makes great sense...but of course, isn't nearly as easy to figure, and will reduce the number of pretties we can have in the tank...(which in reality, isn't a bad idea anyway) __________________ Intelligence is not knowing all the answers, but knowing where and how to find them! www.google.com

07-01-2007, 11:31 AM	#13 (permalink)
Craig Manoukian Regular Guy Moderator Join Date: Nov 2003 Location: Marina Del Ray, CA Posts: 18,179 View Gallery Karma Komment Add yours!	Re: Ye old stocking limit question! Just to let others know I play by the rules; my next tank will be 45 gallons with a 30 gallon refugium and I'm planning a mated pair of Skunk Clowns and three or four Rainsford Gobies (which a very small thin fish) in the display. An Anemone for the clowns, an ornamental clam, and a pair of Harlequin Shrimp will round out livestock other than cleaning crew (nassaurius, turbo and trochus snails, scarlet hermits, fighting conches , and polecheates). This is a minimum bioload for 75 gallons of water total volume. __________________ Currently tankless. 20 Gallon mini reef with mated pair of Maroon Clowns given to Rougiem! 80 gallon reef given to Rougiem/Wooster HS.

09-17-2007, 10:52 PM	#14 (permalink)
ScubaDrew Elegance coral Join Date: Jun 2007 Location: Burlington, VT Posts: 1,043 View Gallery Karma Komment	Re: Ye old stocking limit question! Thanks for the info, its a little dissapointing that in a 92 gal corner I can fit so few fish. Figure 92gal +20 gal sump and refuge - LR - sand = 90 gal. /5gal per inch = 18 inches. My foxface has a max growth of 9inches. leaving me one other fish of similar size. This calculation seems way off from what most other people have listed in tanks of similar size. I like the info, but it seems off compared to what most people practice. __________________ www.NorthEastCoral.com My coral and supply website! STT2VT - Chronical

09-17-2007, 11:04 PM	#15 (permalink)
GeeWizzItsMe See Golden Compass Join Date: Jul 2007 Location: Nashville Posts: 1,857 View Gallery Karma Komment	Re: Ye old stocking limit question! I agree with Scuba. It seems like the only person following this law is Melanie... (Great job!!) I have read in a few books that 1 inch of fully grown fish per gallon is all it takes (thats even without protein skimmer!) Maybe these are old books, but it just seems strange... __________________ VP of Dork Club http://www.reefsanctuary.com/forums/...-new-tank.html

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