What is the ratio of fish to a size of tank?

Question

I mean like having a big selection of size and variety...

Answer 1

And now for tons of people saying 1" to one gallon. That is a totally broken rule and applies to very, very few tanks and very, very few fish. It is a crutch used by people that don't want to be bothered to learn about their fish so they try to apply a over simplified rule to come up with a simple answer to a complex question.

Please don't do this, learn about the fish you want to keep and it's requirements before you by it and then you'll really know if it will be healthy and happy in your tank.

MM

Answer 2

There is absolutely no rule that works for all tanks and all fish, and anyone who simply relies on any "/gallon rule or similar is likely just too lazy, or doesn't know better then, to do actual research the fish they keep.

Here are some reasons why this rule is useless

1. It does not take into account the mass of larger fish. According to this rule I can put a 12" fish in a 12 gallon tank. Common sense predicts otherwise.

2. It does not take into account the aggressive and territorial nature of a fish. According to this rule I can put 4 convict cichlids in a 20 gallon tank. They would kill each other.

3. It does not take into account the activity levels of fish. According to the rule I can put 5 danio's in a 5 gallon tank. A 5 gallon doesn't allow enough room for these speedy creatures.

4. It does not take into account the shape of the tank. According to this rule a tall 30 gallon hex tank with less then 2 sq. ft of surface area and 1.5 ft of length can hold the same number and size of fish as a 30 gallon long tank with 3 sq ft. of surface area and length. Common sense predicts the lack of swimming space in the taller tank leads to lower stocking levels and smaller fish.

5. This rule does not account for how good the fish keeper is at maintaining the tank. Someone who diligently cleans their tank every week can have a more crowded tank, while someone lazy who only cleans it twice per year should really have a very sparse tank.

I'm sure there's other variables I'm forgetting, but hopefully the point is taken - forget rules of thumb, get off your lazy duffs, and actually learn about the fish!

Answer 3

Basically, you want your fish to be able to turn around comfortably at their current size. A very large tank for a very small and compatible population is no harm. It just looks, well, interesting.

As the other more respectful and intelligent responders said, the other factor is the compatibility. Make sure you know what (if any) fish may coexist with each other. As one stated, some tolerate their own kind only. Some abhor their own kind. Some love all that don't attack them. Some love some fish - or at least respect those they cannot beat up. Others don't give a damn and hear the fight bell as soon as ANYTHING comes into the tank - including your hand!

Answer 4

It depends on what types of fish you want to put in the tank. Obviously there are small varieties that don't get very big (like Danios), then there are other types that do get quite large (like Chiclids).
I had goldfish for a long time and the fancy types do get big so their ratio was for every one 1" of the length of the fish, you should have 1 gallon. (include the tail when you measure).
That is how much room they need to grow. I had a 55 gallon tank w/ three goldies and they were big and beautiful. Make sure you don't over-crowd!

Answer 5

If you are talking about the rule of thumb that really shouldn't even be applied to most fish then it is 1 inch of the fishes adult (not the size they are now) size per 1 gallon. But like I said it shouldn't be applied to most fish, oscars shouldn't be in anything smaller then 55 gallons, a fancy goldfish needs 20 gallons and many other fish need a big tank regardless of their size. Look up some info about what ever type of fish you want, most sites will say what the minimum tank size needed is.

Answer 6

Jack M, if you have a betta that is bigger then the average goldfish then you should call up Guinness cause that fish must be huge. Since even the smaller goldfish grow to be around 10" and the common or feeder goldfish grow more then a foot long. While bettas can live in a cup they definitely won't thrive. Stick to turtles cause you obviously no nothing about fish, especially goldfish and bettas. As far as your source, common sense, I guess you are one of the many who don't have any.

I agree that you should look up some information about each type of fish you want, not only to see what size tank they need but to also make sure they are compatible with each other and that you are giving them what they need.

Answer 7

There is no rule of thumb that applies to all fish. 1 inch of fish per gallon is just stupid for most fish. Think of the different shapes, heights, and thicknesses fish come in. That's too variable for that rule to be of any utility.

You need to look at the specific species of fish and their behavior in different size tanks. An oscar or green terror need about 4-5 gallons per inch of the fish minimum as adults whereas you can load up on guppies & tetras where you can get something like 1 inch of fish per gallon.

Look at how piggish the fish is with food. If they eat like pigs (think goldfish or south american cichlids) Then their bodies will be puttitng an awful lot of waste out.

Look at how evil they get when confined in smaller spaces. Some fish need a little room to roam around otherwise they'll make room by killing stuff. Many south american fish will get very aggressive if they even see another fish. Many african fish will be very mean with average # of fish,but if you crowd them out, they will become less aggressive.

Look at how big they'll eventually get at their adult size. If a fish is going to be 14 inches long & your tank is only 13" wide, how's he going to turn around?

Look at specific species charts to figure out how many you can get in a tank.


Two communities of fish that may be easy for you to care for that can bear some overcrowding if you make a mistake, and are colorful are "livebearer" and "african cichlid" communities.

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 (360 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 9

it's not one fish per gallon, it's one INCH of fish per gallon...make sure you count other tank critters, such as crabs, shrimp, frogs, etc....so, for example....i have a 30 gallon tank...i have about 15 fish....since several of them are 2 or 3 inches....if you get more than that, they will start dying...also, make sure you get all fish that are compatible...in my experience, angel fish are mean, and so are gouramis....dont have them in a community tank, unless you have certain varieties, and certain sexes...the pet store can tell you more...i always ask them what i can and cant have :)

Answer 10

The ratio is one gallon of water for every inch of fish.