Inches of fish/gallon rule -- USELESS!

[Don]

I have frequently run across guidelines for the number of fish that
can thrive in a given size aquarium expressed in inches of fish per
gallon. I trust the following assumptions are reasonable:

*Oxygen consumed and waste produced are roughly equivalent to body
mass

*Oxygen consumption and waste production are the primary factors in
determining minimum healthy space requirements for fish.

*The proportions of a fish are similar regardless if the fish is one
inch long or ten inches long.

OK. Body mass is equivalent to the 3rd power of the fish's length.
So 10 fish 1 inch long have only 1/100th the total body mass of 1 fish
10 inches long. Yet according to the frequently quoted rule of thumb
they have the same space requirements! Let's use a little less
extreme example: 10 fish 1 inch long = 10 arbitrary units of mass. 5
fish 2 inches long = 40 of the same units! So we a have discrepancy
of 4/1! That's still way more than enough to render the rule useless.

Is there something I am missing? Seems to me we need to add up the
length of each individual fish taken to the 3rd power and only then do
we have a usable guideline.

Don

[Altum]

Don wrote:
> I have frequently run across guidelines for the number of fish that
> can thrive in a given size aquarium expressed in inches of fish per
> gallon. I trust the following assumptions are reasonable:
>
> *Oxygen consumed and waste produced are roughly equivalent to body
> mass
>
> *Oxygen consumption and waste production are the primary factors in
> determining minimum healthy space requirements for fish.
>
> *The proportions of a fish are similar regardless if the fish is one
> inch long or ten inches long.
>
> OK. Body mass is equivalent to the 3rd power of the fish's length.
> So 10 fish 1 inch long have only 1/100th the total body mass of 1 fish
> 10 inches long. Yet according to the frequently quoted rule of thumb
> they have the same space requirements! Let's use a little less
> extreme example: 10 fish 1 inch long = 10 arbitrary units of mass. 5
> fish 2 inches long = 40 of the same units! So we a have discrepancy
> of 4/1! That's still way more than enough to render the rule useless.
>
> Is there something I am missing? Seems to me we need to add up the
> length of each individual fish taken to the 3rd power and only then do
> we have a usable guideline.

It's worse than that. Your assumptions do not hold. ;-) However, the
formula you have independently found is often very helpful when trying
to understand the difference between one oscar and twelve cardinal tetras.

As for the assumptions...
- Oxygen consumed and waste produced are higher in some families of fish
per gram of body mass than others. Activity levels and tank temperature
also make a difference. And of course, the of the tank determines the
oxygen exchange rate, not the volume.

- The proportions of a fish are not similar regardless if the fish is
one inch or ten inches long. Consider a 3" farlowella catfish vs. a 2"
black moor goldfish.

- Oxygen consumption and waste do not determine a healthy space. All
you need to do is think of a betta in a well-maintained 4" bowl or a 12"
oscar living in a 55 gallon tank that's 13" front to back.

You will find that the more experienced aquarists around here suggest
the 1" per gallon rule to beginners for small (1-2"), slender fish.
It's a heuristic that works reasonably well for tetras, rasboras, barbs,
platies, cories, small gouramis, and many other common beginner fish.

Here's a great article on stocking. http://www.netmax.tk/

--
Put the word aquaria in the subject to email me.
Did you read the FAQ? http://faq.thekrib.com

[Don]

On Sat, 13 May 2006 18:19:16 GMT, Altum >
wrote:

>Don wrote:
>> I have frequently run across guidelines for the number of fish that
>> can thrive in a given size aquarium expressed in inches of fish per
>> gallon. I trust the following assumptions are reasonable:
>>
>> *Oxygen consumed and waste produced are roughly equivalent to body
>> mass
>>
>> *Oxygen consumption and waste production are the primary factors in
>> determining minimum healthy space requirements for fish.
>>
>> *The proportions of a fish are similar regardless if the fish is one
>> inch long or ten inches long.
>>
>> OK. Body mass is equivalent to the 3rd power of the fish's length.
>> So 10 fish 1 inch long have only 1/100th the total body mass of 1 fish
>> 10 inches long. Yet according to the frequently quoted rule of thumb
>> they have the same space requirements! Let's use a little less
>> extreme example: 10 fish 1 inch long = 10 arbitrary units of mass. 5
>> fish 2 inches long = 40 of the same units! So we a have discrepancy
>> of 4/1! That's still way more than enough to render the rule useless.
>>
>> Is there something I am missing? Seems to me we need to add up the
>> length of each individual fish taken to the 3rd power and only then do
>> we have a usable guideline.
>

>It's worse than that. Your assumptions do not hold. ;-)

I realize they are very general and sub ject to other variables. But
I didn't think the margin of error was nearly as bad as the potential
length vs. body mass problem.

I should have said "Everything else being equal."

> However, the
>formula you have independently found is often very helpful when trying
>to understand the difference between one oscar and twelve cardinal tetras.

Surely the 12" Oscar needs more space than the twelve Tetras.

>As for the assumptions...
>- Oxygen consumed and waste produced are higher in some families of fish
>per gram of body mass than others.

Of course.

> Activity levels and tank temperature
>also make a difference.

Of course.

> And of course, the of the tank determines the
>oxygen exchange rate, not the volume.

The typo is that you left out the words " surface area?"
Given different shape tanks and different surface areas per gallon
this makes the formula even worse!

>
>- The proportions of a fish are not similar regardless if the fish is
>one inch or ten inches long. Consider a 3" farlowella catfish vs. a 2"
>black moor goldfish.

I understand there are species variations.

>- Oxygen consumption and waste do not determine a healthy space.

Surely they are important factors.

> All you need to do is think of a betta in a well-maintained 4" bowl

Can there really be such a thing? Or are Bettas just hard to kill?

> or a 12" oscar living in a 55 gallon tank that's 13" front to back.

If the fish cannot turn around that would be a problem.

>You will find that the more experienced aquarists around here suggest
>the 1" per gallon rule to beginners for small (1-2"), slender fish.

So that would sort of work. Even then, there's going to be a huge
difference between 10 1" fish and 5 2" fish.

>It's a heuristic that works reasonably well for tetras, rasboras, barbs,
>platies, cories, small gouramis, and many other common beginner fish.
>
>Here's a great article on stocking. http://www.netmax.tk/

I have not calculated if my 35 gallon tax satisfies the rule or not.
No deaths, fish look good with good appetite, good water chemistry
tests, satisfy me! Of course, African Cichlids are easy -- especially
when you live in Austin, Texas on top of massive limestone deposits
and the water comes out of the tap hard and alkaline.

Don

[Mister Gardener]

On Sat, 13 May 2006 18:19:16 GMT, Altum >
wrote:

>Don wrote:
>> I have frequently run across guidelines for the number of fish that
>> can thrive in a given size aquarium expressed in inches of fish per
>> gallon. I trust the following assumptions are reasonable:
>>
>> *Oxygen consumed and waste produced are roughly equivalent to body
>> mass
>>
>> *Oxygen consumption and waste production are the primary factors in
>> determining minimum healthy space requirements for fish.
>>
>> *The proportions of a fish are similar regardless if the fish is one
>> inch long or ten inches long.
>>
>> OK. Body mass is equivalent to the 3rd power of the fish's length.
>> So 10 fish 1 inch long have only 1/100th the total body mass of 1 fish
>> 10 inches long. Yet according to the frequently quoted rule of thumb
>> they have the same space requirements! Let's use a little less
>> extreme example: 10 fish 1 inch long = 10 arbitrary units of mass. 5
>> fish 2 inches long = 40 of the same units! So we a have discrepancy
>> of 4/1! That's still way more than enough to render the rule useless.
>>
>> Is there something I am missing? Seems to me we need to add up the
>> length of each individual fish taken to the 3rd power and only then do
>> we have a usable guideline.
>
>It's worse than that. Your assumptions do not hold. ;-) However, the
>formula you have independently found is often very helpful when trying
>to understand the difference between one oscar and twelve cardinal tetras.
>
>As for the assumptions...
>- Oxygen consumed and waste produced are higher in some families of fish
>per gram of body mass than others. Activity levels and tank temperature
>also make a difference. And of course, the of the tank determines the
>oxygen exchange rate, not the volume.
>
>- The proportions of a fish are not similar regardless if the fish is
>one inch or ten inches long. Consider a 3" farlowella catfish vs. a 2"
>black moor goldfish.
>
>- Oxygen consumption and waste do not determine a healthy space. All
>you need to do is think of a betta in a well-maintained 4" bowl or a 12"
>oscar living in a 55 gallon tank that's 13" front to back.
>
>You will find that the more experienced aquarists around here suggest
>the 1" per gallon rule to beginners for small (1-2"), slender fish.
>It's a heuristic that works reasonably well for tetras, rasboras, barbs,
>platies, cories, small gouramis, and many other common beginner fish.
>
>Here's a great article on stocking. http://www.netmax.tk/

Here's what I've been chewing on and getting no where - when a tank,
say a 55, has 2-3 inches of gravel on the bottom, how does that change
the tank size in relation to rules of fishes per inch and watts per
gallon. I assume the presence of gravel and ornaments aren't
considered when applying those rules?

-- Mister Gardener
-- Pull the WEED to email me

[John Allen]

Inche per gallon is a myth. What matters is the type and efficency of the
filter system you have. Look at dealers and breeders tanks - excellent
filtration and water quality means the water can sustain more fish.



"Don" > wrote in message
...
>I have frequently run across guidelines for the number of fish that
> can thrive in a given size aquarium expressed in inches of fish per
> gallon. I trust the following assumptions are reasonable:
>
> *Oxygen consumed and waste produced are roughly equivalent to body
> mass
>
> *Oxygen consumption and waste production are the primary factors in
> determining minimum healthy space requirements for fish.
>
> *The proportions of a fish are similar regardless if the fish is one
> inch long or ten inches long.
>
> OK. Body mass is equivalent to the 3rd power of the fish's length.
> So 10 fish 1 inch long have only 1/100th the total body mass of 1 fish
> 10 inches long. Yet according to the frequently quoted rule of thumb
> they have the same space requirements! Let's use a little less
> extreme example: 10 fish 1 inch long = 10 arbitrary units of mass. 5
> fish 2 inches long = 40 of the same units! So we a have discrepancy
> of 4/1! That's still way more than enough to render the rule useless.
>
> Is there something I am missing? Seems to me we need to add up the
> length of each individual fish taken to the 3rd power and only then do
> we have a usable guideline.
>
> Don

[Altum]

Don wrote:
> On Sat, 13 May 2006 18:19:16 GMT, Altum >
> wrote:

<snip>

>> And of course, the of the tank determines the
>> oxygen exchange rate, not the volume.
>
> The typo is that you left out the words " surface area?"
> Given different shape tanks and different surface areas per gallon
> this makes the formula even worse!
>
ROFLMAO! Nice catch. I've got to stop cutting and pasting....

>> - The proportions of a fish are not similar regardless if the fish is
>> one inch or ten inches long. Consider a 3" farlowella catfish vs. a 2"
>> black moor goldfish.
>
> I understand there are species variations.
>
>> - Oxygen consumption and waste do not determine a healthy space.
>
> Surely they are important factors.

Granted they are the most important limiting factors. Fail to meet
oxygen consumption and waste and the fish dies. But two male bettas in
one ten gallon tank are equally dead. ;-) As are tiny neons in a ten
gallon tank with an adult angel. I also consider these situations
"stocking" issues.

>> All you need to do is think of a betta in a well-maintained 4" bowl
>
> Can there really be such a thing? Or are Bettas just hard to kill?

Yes, there can really be such a thing. Put some fine gravel in the bowl
and you can grow enough nitrifying bacteria to have ammonia control.
Change water every 24-48 hours and nitrates, DOC, etc. stay well under
control. It's a cramped life for the fish, but the parameters of oxygen
and water quality can be met.

>> or a 12" oscar living in a 55 gallon tank that's 13" front to back.
>
> If the fish cannot turn around that would be a problem.
>
>> You will find that the more experienced aquarists around here suggest
>> the 1" per gallon rule to beginners for small (1-2"), slender fish.
>
> So that would sort of work. Even then, there's going to be a huge
> difference between 10 1" fish and 5 2" fish.

Yes. Fortunately, the five 2" fish situation works fine with this rule.

>> It's a heuristic that works reasonably well for tetras, rasboras, barbs,
>> platies, cories, small gouramis, and many other common beginner fish.
>>
>> Here's a great article on stocking. http://www.netmax.tk/
>
> I have not calculated if my 35 gallon tax satisfies the rule or not.
> No deaths, fish look good with good appetite, good water chemistry
> tests, satisfy me! Of course, African Cichlids are easy -- especially
> when you live in Austin, Texas on top of massive limestone deposits
> and the water comes out of the tap hard and alkaline.

Great! Somehow most people who keep fish successfully develop an
intuitive feel for correct stocking.

--
Put the word aquaria in the subject to email me.
Did you read the FAQ? http://faq.thekrib.com

[-ED]

On Sat, 13 May 2006 14:38:30 -0500, Mister Gardener
> wrote:

> On Sat, 13 May 2006 18:19:16 GMT, Altum >
> wrote:
>
>> Don wrote:
>>> I have frequently run across guidelines for the number of fish that
>>> can thrive in a given size aquarium expressed in inches of fish per
>>> gallon. I trust the following assumptions are reasonable:
>>>
>>> *Oxygen consumed and waste produced are roughly equivalent to body
>>> mass
>>>
>>> *Oxygen consumption and waste production are the primary factors in
>>> determining minimum healthy space requirements for fish.
>>>
>>> *The proportions of a fish are similar regardless if the fish is one
>>> inch long or ten inches long.
>>>
>>> OK. Body mass is equivalent to the 3rd power of the fish's length.
>>> So 10 fish 1 inch long have only 1/100th the total body mass of 1 fish
>>> 10 inches long. Yet according to the frequently quoted rule of thumb
>>> they have the same space requirements! Let's use a little less
>>> extreme example: 10 fish 1 inch long = 10 arbitrary units of mass.. 5
>>> fish 2 inches long = 40 of the same units! So we a have discrepancy
>>> of 4/1! That's still way more than enough to render the rule useless.
>>>
>>> Is there something I am missing? Seems to me we need to add up the
>>> length of each individual fish taken to the 3rd power and only then do
>>> we have a usable guideline.
>>
>> It's worse than that. Your assumptions do not hold. ;-) However, the
>> formula you have independently found is often very helpful when trying
>> to understand the difference between one oscar and twelve cardinal
>> tetras.
>>
>> As for the assumptions...
>> - Oxygen consumed and waste produced are higher in some families of fish
>> per gram of body mass than others. Activity levels and tank temperature
>> also make a difference. And of course, the of the tank determines the
>> oxygen exchange rate, not the volume.
>>
>> - The proportions of a fish are not similar regardless if the fish is
>> one inch or ten inches long. Consider a 3" farlowella catfish vs. a 2"
>> black moor goldfish.
>>
>> - Oxygen consumption and waste do not determine a healthy space. All
>> you need to do is think of a betta in a well-maintained 4" bowl or a 12"
>> oscar living in a 55 gallon tank that's 13" front to back.
>>
>> You will find that the more experienced aquarists around here suggest
>> the 1" per gallon rule to beginners for small (1-2"), slender fish.
>> It's a heuristic that works reasonably well for tetras, rasboras, barbs,
>> platies, cories, small gouramis, and many other common beginner fish.
>>
>> Here's a great article on stocking. http://www.netmax.tk/
>
> Here's what I've been chewing on and getting no where - when a tank,
> say a 55, has 2-3 inches of gravel on the bottom, how does that change
> the tank size in relation to rules of fishes per inch and watts per
> gallon. I assume the presence of gravel and ornaments aren't
> considered when applying those rules?
>
>
And remember, a 55gal is really only around 47gal. Then figure gravel
height into the mix, add(substract)in the decor displacements, a deck of
cards, and we could have a swell evening!
--
Thanks-ED

[Koi-Lo]

Yep sure is useless, just like Carol and the groups are
becoming.......USELESS
Can you say thank you Carol Gulley

==============================================
Put some color in your cheeks...garden naked!
"The original frugal ponder.."Since my statements are
given freely, take em or leave em, I am entitled to
my opinion none the less. My opinion and $1 is still
only worth $1.....but I am entitled to "MY" opinion...
~~~~ }<((((o> ~~~~~~ }<{{{{o> ~~~~~~~ }<(((((o>

[-ED]

On Sat, 13 May 2006 14:53:13 -0500, John Allen
> wrote:

> Inche per gallon is a myth. What matters is the type and efficency of the
> filter system you have. Look at dealers and breeders tanks - excellent
> filtration and water quality means the water can sustain more fish.
>
>
And we've yet to dicuss the mental health of the tank's occupants and the
relativity of stress vs. well-being.
Whew !!!what did I just open up =)
--
Thanks-ED

[Koi-Lo]

Oh, do you now have Carol in a dam fish tank? I csan see where
mental is a problem since your dealing with her.

On Sun, 14 May 2006 01:27:43 GMT, -ED > wrote:
>><>On Sat, 13 May 2006 14:53:13 -0500, John Allen
> wrote:
>><>
>><>> Inche per gallon is a myth. What matters is the type and efficency of the
>><>> filter system you have. Look at dealers and breeders tanks - excellent
>><>> filtration and water quality means the water can sustain more fish.
>><>>
>><>>
>><>And we've yet to dicuss the mental health of the tank's occupants and the
>><>relativity of stress vs. well-being.
>><>Whew !!!what did I just open up =)


==============================================
Put some color in your cheeks...garden naked!
"The original frugal ponder.."Since my statements are
given freely, take em or leave em, I am entitled to
my opinion none the less. My opinion and $1 is still
only worth $1.....but I am entitled to "MY" opinion...
~~~~ }<((((o> ~~~~~~ }<{{{{o> ~~~~~~~ }<(((((o>

[Koi-Lo]

On Sun, 14 May 2006 01:20:46 GMT, Altum >
wrote:
>><>Don wrote:
>><>> On Sat, 13 May 2006 18:19:16 GMT, Altum >
>><>> wrote:
>><>
>><><snip>
>><>

>><>>
>><>ROFLMAO! Nice catch.
>><>
snip

Carol caught something a few times, THE CLAP!

==============================================
Put some color in your cheeks...garden naked!
"The original frugal ponder.."Since my statements are
given freely, take em or leave em, I am entitled to
my opinion none the less. My opinion and $1 is still
only worth $1.....but I am entitled to "MY" opinion...
~~~~ }<((((o> ~~~~~~ }<{{{{o> ~~~~~~~ }<(((((o>