The dreaded 1 inch per gallon rule

[cherule]

Hi all,
I just got my April issue of Aquarium Fish International and saw an interesting bit of info that explains more completely the implications of this 'rule'.

"An old rule of thumb says that you can keep 1 inch of fish per gallon of water. Unfortunately, this rule only applies to small fish 3 inches or less. The rule does not apply to large fish. As a fish grows, it increases in length, width and height. A 10-inch fish is 10 times as long as a 1-inch fish...but it's also 10 times as wide and 10 times as high. Effectively, a 10-inch fish is 1,000 times larger than a 1-inch fish. One 10-inch fish eats a lot more food and excretes a lot more waste than 10 1-inch fish."

They also have a table that makes it even more clear:

Inches in length = this many fish in mass
1 ==== 1
2 ==== 8
3 ==== 27
4 ==== 64
5 ==== 125
6 ==== 216
7 ==== 343
8 ==== 512
9 ==== 729
10 === 1,000
11 === 1,331
12 === 1,728
24 === 13,824!! :eek3:

This is a lot better way of thinking about the 1-inch rule, don't you think? Very interesting anyway!!

 

[Fishy_Fun]

hmm thats very interesting especially the last one:lipssealedsmilie:

 

[Danyal]

so then a 24" fish is going to need a 13,800g tank? i'm so freakin tired of these crappy rules.

 

[Tolak]

Stocking is just as much art as science, if not more so. It is an interesting perspective, but stocking is nowhere near a mathematical equation.

 

[Tolak]

Someone just brought this to my attention, very similar; http://www.star-trek-voyager.net/ship4/warp_factors.htm#chart

 

[Mgamer20o0]

they shouldnt even talk about it lol

 

[Coler]

its garbage

 

[kimmisc]

The numbers are what the fish are equivalent to in fish mass, not the gallons suggested. A 10 inch fish is equivalent to 1000 1" fish (with size and bio-load considered), not 10 inches of fish, and not 1000 gallons of water. Not that I'm agreeing or disagreeing with their theory.. just clarifying.

Their theory may not be dead on accurate, but it would cause many less disasters than the old inch per gallon rule.

 

[Dave-ZZ4]

I can understand where they are going with it but it is as inaccurate as the 1" per gallon rule as well. It all depends on the fish. The way it should be is 1 gallon per cubic inch of fish. using a 6" Cichlid as an example:

Typically it would be 6" long about 4.0" high and about 1.5" wide.

1G per 1" = a minimum 6 gallon tank (too small)
By table above it needs to be a minimum 216 gallon tank.

1G per cubic inch = a minimum 36G tank

A fully grown Oscar at 12" long 6" high and 3" wide would require a 216 gallon tank where by the chart above you would need a 1,728 gallon tank.

Anyhow, that's just my opinion and that is how I usually set up my tanks for stocking.

As for fish waste, That would deal more with filtration rather than tank size.

 

[kimmisc]

The end product of fish waste is nitrates, which has plenty to do with tank size because of dilution.