If the 1 in./gal rule isn't always good, what if?

Question

I've heard that rule (1 in./gal) in stocking freshwater is not always reliable, whats a good way to stock one's tank then?

Answer 1

Common Glass Aquarium Sizes

5.5 Gallon 16x8x10 (128 sq. in.)
10 Leader 20x10x12 (200 sq. in.)
10 Hexagon 14x12x18 (127 sq. in)
15 Gallon 24x12x12 (288 sq. in.)
20 High 24x12x16 (288 sq. in.)
20 Long 30x12x12 (360 sq. in.)
25 Gallon 24x12x20 (288 sq. in.)
29 Gallon 30x12x18 (360 sq. in.)
30 Gallon 36x12x16 (432 sq. in.)
30 Breeder 36x18x12 (648 sq. in.)
33 Long 48x13x12 (624 sq. in.)
37 Gallon 30x12x22 (360 sq. in.)
38 Gallon 36x12x20 (432 sq. in.)
40 Long 48x13x16 (624 sq. in.)
40 Breeder 36x18x16 (648 sq. in.)
45 Gallon 36x12x24 (432 sq. in.)
50 Gallon 36x18x18 (648 sq. in.)
55 Gallon 48x13x20 (624 sq. in.)
65 Gallon 36x18x24 (648 sq. in.)
Petite body fish
1” per gallon or 1” per 12 sq. in. of surface
For example 20 long has 360 sq. in. surface area
360/12=30
Can a 20 long support 30” of fish? Probably not.
A 20 high has only 288 sq. in. surface area
288/12=24
Can a 20 high support 24” of fish? Probably not.
A 25 is also 288 sq. in. surface area
288/12=24
Can a 25 support 24” of fish? Probably.
I like to average the two for a more accurate capacity.
For the 20 long, 30 by surface area, 20 by volume averages to 25”
Can a 20 long support 25” of fish? Probably.
For the 20 high, 24 by surface area, 20 by volume averages to 22”
Can a 20 high support 22” of fish? Probably.
Why does the 20 long support 3” more fish that the 20 high?
A larger surface area allows a greater oxygen exchange, which is as important as volume of water.
Large bodied fish, such as gold fish you need to double or even triple these numbers, i.e. 3 gallons per inch and 36 sq. in. of surface per 1” of fish.
This is not the only consideration for fish tanks. Types of fish will appreciate one type of tank over another. For example, fast swimmers like Zebra Danios, Pearl Danios and Blue Danios will do best in a tank that is at least 30” long. They would be better kept in a 20 long rather than a 25. Giant Danios would do best in a tank at least 48” long. They would be better kept in a 55 rather than a 65.
On the other hand, slow, tall bodied fish like Angel Fish and Discus will do best in a deep tank. They would be better kept in a 65 rather than a 55. They, like other cichlids also need a bit more than the 1” per gallon and/or 12 sq. in. surface.

Answer 2

The one inch per gallon rule of thumb is pretty good for non territorial tropical fish. A 2 inch wide fish vs a 1/4 inch wide fish will obviously need a different scale. Another thing is to always check the water quality. The slower you raise the stock in your tank, the easier it is for the tank to handle it, even if it's more than would normally be handled in a tank that size. This is how fry do not really effect the bio load and if they grow slowly have a minimal effect. The problem as they grow is the waste production.

Answer 3

Part of the problem with the 1 inch/gallon rule is that people often don't know (or like) that it only applies to small, slender fish like guppies and tetras. As fish get bigger than that, they need more room for territory and for waste production. Solving that means doing research on each individual fish you want to buy, either by reading books, or by googling and cross-checking lots of different websites for accuracy, or by consulting reliable, experienced fishkeepers.

Even for small fish, the inch/gallon rule tends to break down when tanks are in non-standard shapes, like hexagons or cubes. That's because the surface area is different in proportion to the volume. More surface area = more oxygen for fish. Less surface area = less oxygen for fish.

Find the surface area of your tank by multiplying the length and width of your tank. Then divide that by 12, which will give you how many inches of small, slender fish you should be able to stock.

Answer 4

1inch of fish per 12sq inch's of surface area, this 1in of fish has been made up by some sadistic fish shop owner to sell more fish, the above rule pertaining to surface area is a guide as you can obviously cram more in if they re the right sort of fish, or cannot put that amount in if its the wrong sort of fish if you see what i mean.
If you have a tank full of gourami's which have the ability to breath atmospheric air then its not as difficult to place more than 1in per in your tank however,
If its 2 tiger Oscar's then they're messy large fish and really require more room and oxygen than the rule applies too.
If you have a planted tank for the whole system to balance you need probably 50pct less fish for it too work and so on so there is really nothing set in stone only a guide. and it ain't 1in per gallon.

AJ

Answer 5

With modern filtration systems and proper maintenance (regular water changes etc.) an inch of fish per gallon of water is really a pretty good rule of thumb. You just have to take into consideration that it's 1 inch per gallon based on the expected adult size of the fish - not the size it is when you buy it at the pet store.

Answer 6

Here are the main fish stocking parameters i observe and pass on to my clients:

*The amount of surface area relative to the gallons of water the aquarium holds. I have observed many tall narrow aquariums over the years of my maintenance service where the filtration and other factors were equal to comparable sized and stocked rectangular aquariums, that general fish health and longevity were lower.

*Type of fish, such as fish that naturally produce more waste (partly do to the type of food they eat) such as goldfish where one fish per 8+ gallons is better. Also a fish such as an Arowana that stays primarily on the surface will need a disproportionately large aquarium (I recommend 200 + gallons for just one Arowana). You cannot compare a heavy bodied cichlid for instance to a narrow bodied tetra of similar length.

*Filtration, a properly filtered aquarium (good bio filtration, good mechanical filtration, and good circulation) with multiple filters is important.

*Maintenance schedule that includes regular efficient water changes

*Well maintained water chemistry (including kH and Redox)

*New or experienced aquarist; a new aquarist needs to start with a much less crowded aquarium.

*After proper feeding, good cleaning routines (20% water changes with a gravel vacuum once per week or two), proper feeding routines, good filtrations; If after all these are checked off and you still have nitrates that struggle to stay below 40-50 ppm, you probably have an over stocked aquarium (especially if there are live plants!). Also a kH and pH that starts out at proper levels, but then drops quickly after water changes and/or addition of stabilizing chemicals or products such as Wonder Shells can indicate over stocking (as well as other problems such as mulm buildup).

For more information about FW aquarium basics, i recommend reading this article:
http://www.americanaquariumproducts.com/Basic_Aquarium_Principles.html

Answer 7

It's valid to a certain extent.

Picture an 8 inch Blood Parrot Cichlid in an 8 gallon tank...

Now picture 4 two inch Guppies in an 8 gallon tank.

See what I mean?


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Answer 8

If you wish to keep more fish than 1 inch per gallon, which is a crappy rule, it helps to balance your tank. Don't keep only bottom dwelling fish, they will get very territorial. If you were to buy fish that would stay to bottom, middle, or the top of the tank, you can keep more fish than if you only had fish that would stay in one area. If you keep live plants and hiding places, the number of fish rises. If you provide more filtration, vacuuming, and surface agitation/area, you can keep more fish. Longer, wider tanks will always support more fish than a tall tank.

Get groups of top level swimmers, middle swimmers, and bottom dwellers. Give them space to spread out. Like somebody implied about guppies and Oscars, use common sense.

Answer 9

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Answer 10

One inch of fish per 12 SQUARE inches.