fish/tank ratio?

Question

does anyone know or know where to find a chart that says how many inches of fish you can have in a certain size tank...someone told me it was 1 inch per gallon and someone else told me it wasnt that im just trying to find a chart or a equation of some sort to figure it out...please help thanks

Answer 1

I think Sandy has the best analysis of this.

Basically you see this one inch of fish rule becasue like yourself, people need something to estimate by, and that's all it is, is just an esitmate. I try to aim more for accuracy and I'm going to help you with that.

First things first, needed to know is your tank size for one, particularly, the dimensions. Then what particular fish you are interested in. We can solve compatibility as it goes because if I see the logic or though to keeping a species, if one is too big or incompatible, an alternative can be reccomended. Based on these two factors first, then you look at what you can put in.

The one inch rule doesn't work simply because of the main reasons Sandy pointed out. If you say it's one inch of fish per gallon, that says I can keep a 14 inch Oscar and add more then that to a 20 gallon tank...but think about that. Does that make sense to do? Consideration there is space to move, and waste production along with the overall girth of that fish, it just won't work and would die. Now by that same token, could I put 20 neon tetras in a 20 gallon tank? Sure, and then some. But why? First on a neon tetra, that's a schooling fish and they do much better off in bigger numbers at least 7 but higher will work. Second, fish that size don't have much overall mass to them, wouldn't occupy alot of overal surface area in the tank, and don't produce on the same scale of the Oscar, nearly as much waste so that would work.

If one is to simply say one inch of fish, add the size and put, you're going to have many fish funerals I think. One thing this is not directly addressing but important, that four inch fish you buy at the pet store or wherever, find out is that the adult size for that fish or not. Odds are you are not buying a fully grown adult fish and that fish you buy today is not going to stay that size, so when estimating your overall population consider end size aka adult size for whatever species you want to add.

There's more that could be said here but for brevities sake, if you need futher information you can always email me direct, or you can also go to fishless cyling.com. Full staff on hand to take care of anything you need answered. You can use the link on my profile as well.

JV

Answer 2

Fish To Gallon Ratio

Answer 3

Great job everyone. Phew i'm just happy that there are many people here too that believe the one inch rule is soo inaccurate. Anyhow Sandy's got most of it down pat! awesome but i would like to add ONE more thing. Don't forget about your filtration system. As long as your filtration system can handle the bioload that your fish brings into the tank then with everything else kept in mind, you should be able to maintain a stable tank. I believe there's some arguments that you should go for up to 3x the gallons per hour output that your tank can hold. (ex. 50 gallons.. go for a 150 gallons per hour filter) but then you also have to think about the kind of current that it'll create in your tank. I may not be correct with the ratio but keep in mind filtration and bioload! Try asking questions at aquariacentral.

Answer 4

Thats a very generic rule. There is no standard rule since a stable number of fish in a tank is determined by a number of factors:
Size of Fish
Agressiveness of Fish
Activeness of Fish
Tank Occupation Area (For example, you can have top swimming fish, bottom swimming...)

My suggestion would be to plan out your tank before hand. Try to find a nice balance. You can use the 1inch per rule as a guideline, but take into consideration other factors. However the 1inch rule can fail. You never want to place a 35" fish in a 35 Gallon tank. They wouldn't even have enough room to turn around.

If you want to take your tank planning a step further than I would recommend joining a fish forum site. You can ask specific questions and they can help you with small details.

Answer 5

There is no equation that really works consistently. Right now, I have almost 30 inches of fish in my 10 gallon tank, but my fish all enjoy separate levels of the water column and I do weekly maintenance. It depends on what kind of fish you want. Email me with the specifics and I will help you as much as I can. Also, the link in my profile is really helpful.

Nosoop4u

The "1 inch of fish per gallon of water" rule is horrible. By that rule, you could put a fish that is a foot long, in a 12 gallon tank. The fish wouldn't even be able to move!

Answer 6

Just to underline how inaccurate and useless the "1 gallon per inch of fish", would you put a 10 inch fish in 10 gallons of water?

Answer 7

It depends on the species of fish.

Gold fish, which are really dirty, should have at least 2 gallons for every inch, same with salt water fish because they are very sensitive to water quality.

Smaller freshwater fish do well on the 1 inch per gallon rule.

I'm not sure about larger freshwater fish, like the large cichlids.

Just remember to take into consideration their full adult size, not the size they are as babies.

Answer 8

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. There is no way you're going to keep a 10" Oscar in a 10 gallon tank. Larger fish tend to need more space in relation to their size and activity levels.
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 9

Not only can the salinity vary for a brackish tank,it should vary,to accurately immitate the conditions encountered by the fish in the wild.The website mentioned in the first answer will give you some parameters.

Answer 10

While there are all sorts of myths, there is no across-the-board, blanket rule that covers all fish. You need to look at each fish individually according to the different aspects listed by Sandy above (oh, also, whether the fish is a schooling fish is another consideration). You just have to look at all the different fish you are interested in and see what their water requirements are as well as their compatibility with the other fish you're considering.