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I found this in a rather large advertisement in an Aust National Gardening Magazine.
Burke's Backyard Dec 2007/Jan 2008

The ideal amount of space for each fish is 2cm of fish, excluding the tail, for every 200 square centimeters of surface area.
A 23Lt tank with a large surface area will support 3-4 fish providing there is good filtration and plenty of partial water changes.
Fish do grow but it is a slow process and it will take them a long time to outgrow their tanks. Fish that live in ponds grow a lot faster.

I am not saying if this is correct or incorrect but it raises some different and interesting points compared to the old 1 inch of fish per Lt or Gal as I have also seen it.

This now makes it a surface area not a capacity measurement. A point to consider when getting a tall tank which has same capacity but a big difference in surface area.

It also mentions filtration and water changes not usually seen in this type of "How many" calculation.

It also mentions growth of the fish.

How about some interesting comments.

I will also point out in a add for a 5.7 Lt tank it has 6 Goldfish in it

Have a look in [link=My Profile] http://www.fishprofiles.com/forums/member.aspx?id=1935[/link] for my tank info

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Betta 11Gal Desktop & Placidity 5ft Community Tank Photos

Keith

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OK... so for my 6 foot long 180 gal tank the calculations would be as follows:

Surface area: 180cm x 60cm = 10,800 sq cm. If I divide that by 200 to get the number of 2 cm fish I could theoretically keep... 10,800 / 200 = 54 (2 cm fish)

That's vastly different to the old 1 inch per gallon theory, which would allow 228.5 x 2cm fish (or 180 x one inch fish)

I don't necessarily subscribe to either theory as I think there are a lot of other factors involved when determining appropriate stocking levels for a tank, but it's an interesting comparison.

G_T

Never be afraid to try something new. Remember that a lone amateur built the Ark. A large group of professionals built the Titanic.

the problem with both those rules are

inch per gal
1. Doesnt incorporate surface area allowing you to have alot of fish in little but tall tanks


surface area
1. doesnt incorperate the depth of the water so theoretically you would have as many fish in a 1cm deep tank as a 4ft high tank with the same footprint

Both
1.Doesnt incorperate the amount of waste produced by the fish for example a BN produces alot more waste then say 4 neons would
2.Doesnt incorporate the individual fish for instance an altum angelfish would work better in a 50g tall tank rather then a 50breeder

I think if someone could create a formula and took the principles from both and combined them together you could get fairly close to an accurate stocking measurement but even then you would have to take the types of fish into account.

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''All the clown fish and yellow tangs in the world cant save you now!''

I think if someone could create a formula and took the principles from both and combined them together you could get fairly close to an accurate stocking measurement but even then you would have to take the types of fish into account.

First off, it would be awesome to have somebody create a rule like that, but it would take some time to figure out. I can foresee someone doing it though, and i am sure that somebody has an accurate rule of thumb that they might not have published. We will have to wait until he/she does indeed publish it!

I agree, The only really true way to tell is by actually measuring how much food the fish eat, and how much waste they produce, plus wayy more factors. And the feel for the stocking max comes with experience and years in the hobby.

Fish do grow but it is a slow process and it will take them a long time to outgrow their tanks. Fish that live in ponds grow a lot faster.

Just a comment on that. Wont the fish Not grow in a small tank? A 24lt is only like what, a 5-6gal tank? I would only put very small fish in such a small area. Even so, you would have to do a lot of water changes, in order to have 3-4 fish. Only really small bodymass fish, like neon tetras or danios would work.

Over all though, i think it is not as accurate as we want it, and way more harder to measure than the 1 inch per gallon rule, but it is a tad bit more accurate. Its just that a begginner who does not have such a wonderful site to turn to would not want to go through the trouble of measuring each fish, and doing water changes, etc. I think there should be an accurate rule of measuring biomass and waste production, and incorporate it with the gallon, and surface area rule.

Lets see some more ideas!

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The ideal amount of space for each fish is 2cm of fish, excluding the tail, for every 200 square centimeters of surface area.
A 23Lt tank with a large surface area will support 3-4 fish providing there is good filtration and plenty of partial water changes.
Fish do grow but it is a slow process and it will take them a long time to outgrow their tanks. Fish that live in ponds grow a lot faster.

this exact paragraph was in a panphlet that came with an aquarium i bought. cheap 70 litre tank from big W. i bought it for au$200 (it was the last one left) and i went there yesterday and they had heaps of them for au$148 each

Fish do grow but it is a slow process and it will take them a long time to outgrow their tanks. Fish that live in ponds grow a lot faster.

yeah they would grow slow because they would be stunted. if you put an oscar in a 23liter tank it would grow slower than if it were in an adequately sized 300liter tank because it would ajust to the size of the tank but it will still try to grow and may reach an unhealthy 7-8" and would be extremly cruel.

A 23Lt tank with a large surface area will support 3-4 fish providing there is good filtration and plenty of partial water changes.

so this would mean i could put say, 3-4 1-2" silver dollars in a 23 litre tank? they would still grow and probably end up destroying the tank

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keep in mind Keith is not advocating this stocking method merely putting it out there to liven things up and perhaps attain some aquatic enlightenment.

I also believe its implying that you should up-size the tank when the 2cm of fish per 200cm2 is broken this fundamentally means that the 23L tank would be able to support an oscar of around 7cm personally i dont think the oscar would stunt at that size in that tank. But for an oscar or similar fish to get to 7cm it doesnt take much time at all so youd be upgrading the tank pretty quick

and no bubblebrain it wouldnt mean 3-4 1-2inch silver dollars could go in a 23L tank it would mean you could have 3 one inch silver dollars or 2 one and a half inchers

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''All the clown fish and yellow tangs in the world cant save you now!''

I use the Surface area measurements myself. In a book I have here It also says that, the amount of surface area per fish (adult size) depends on the type of tank set up as well.

Taken from the book these are the measurements.

Tropical Freshwater for 1 inch of fish 12sq inches (75 sq cm)
Cold water Fresh " 28 sq inches (180 sq cm)
Tropical Marine " 47 sq inches (300 sq cm)

It doesn't list the Cold water Marine measurements.

It also says of course that it also depends on the fish themselves.

I don't stay strictly with the guidelines, but I use them as a general rule of thumb.

(This info comes from the Aquarium Owners Manual by Gina Sandford for those interested in reading exactly what was written.)

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