Average Fish Weights and
Pond Stocking Levels
Koi and Pond Fish Weight Chart
To Use This Chart Correctly:
- Calculate the Total Specific Surface Area (SSA) of your biological filter.
- Calculate the Total Fish Waste your biological filter can metabolize per day.
- Multiply the Total Fish Waste by The 1,000 Gallon Factor to determine the Max Fish Weight your biological filter, pond, and water volume can support.
- Divide the Max Fish Weight by the length of the fish in your pond.
Jump directly to the Fish Weight chart below
What is Specific Surface Area (SSA), and Why is it Important?
Filter Media Specific Surface Area (SSA) Charts
Find your SSA, fish waste, and total fish weight your filter can support here
Example: The Ahi Hydro Vortex™ filter is rated to support 406.20 grams of fish. The average weight of a 6" pond fish is 59.25 grams. Divide 406.20 by 59.25 which equals 6.86 or about 6½ 6" fish. Or 23 4" fish. (406.20 / 17.58 = 23.11)
Below is a conservative listing of the "average" weight of pond fish by size. Pond fish include Koi, goldfish, shubunkins, and other types. Use this information to get a basic idea of how many fish your biological filter can effectively metabolize. Your fish may be heavier, or lighter for its size than these average weights. Also, many factors affect the Metabolization rate of your pond - in addition to your biological filter - such as amount of aquatic plants, gravel, rocks, sun, shade, etc. Use this chart as a reference for comparing different brands of biological filters.
NEVER BASE YOUR FISH STOCKING LEVELS SIMPLY BY GALLONS OF WATER, SQUARE FOOTAGE OF THE POND, OR LENGTH OF THE FISH!
If someone tries to tell you that you can have 1" of fish per square foot of pond water, or 1" of fish per 10 gallons of pond water, they are incorrect. Fish weight increases exponentially as they grow.
Example: You have a 100 square foot pond, and someone tells you that you can have 100" of fish in the pond. (based on the incorrect, but popular formula of 1" of fish per square foot of pond water) That could mean 100 1" fish, or 10 10" fish, or 20 5" fish. How do you know which will be correct? What happens when the fish grow? The health of your fish depends on you being correct.
Fish produce waste and ammonia based on their weight - not their length. Their weight dramatically increases as they grow in length - thus the larger they get, the more waste they create. You can see from the chart below that one 10" fish weighs 274.99 grams but ten 1" fish combined only weigh 2.80 grams. The 10" fish produces 82.50 grams of waste per day, but the ten 1" fish combined produce only .84 grams.
Fish produce an average of .3 of their weight in waste per day.
The SSA of your filter will tell you how much total fish weight, and fish waste in can metabolize in a 24 hour period. The chart below helps you understand what sizes, and quantities of fish your filter can support.
You MUST know the Total SSA of your filter to know how many fish you can place in your pond!
Fish Weights and Lengths
Fish Length |
Weight in Ounces |
Weight in Grams |
1" |
.01 |
.28 |
2" |
.08 |
2.27 |
3" |
.26 |
7.37 |
4" |
.62 |
17.58 |
5" |
1.21 |
34.30 |
6" |
2.09 |
59.25 |
7" |
3.33 |
94.40 |
8" |
4.96 |
140.61 |
9" |
7.07 |
200.43 |
10" |
9.70 |
274.99 |
12" |
16.76 |
475.14 |
14" |
26.61 |
754.38 |
16" |
39.72 |
1,126.04 |
18" |
56.55 |
1,603.17 |
20" |
77.58 |
2,199.36 |
22" |
103.25 |
2,927.10 |
24" |
134.05 |
3,800.25 |
26" |
170.43 |
4,831.61 |
28" |
212.87 |
6,034.76 |
30" |
261.82 |
7,422.47 |
Remember, when comparing biological filters, it is important to know the bacteria Specific Surface Area (SSA) it has. This allows you to compare "apples to apples" as the SSA is the most important part of the biological filter. The SSA enables you to calculate the total fish waste it can metabolize, and the total number of fish - by size - that the filter can support.
If the biological filter you are looking at doesn't provide you with basic SSA information, you should question why that manufacturer is withholding that information from you. Its your pond, and they're your fish.....you deserve to know what that filter can support.
The most common problems of excessive algae, and sick fish are directly related to improperly sized biological filters - filters with low SSA numbers. Before purchasing a pond kit that includes a biological filter, or a stand-alone biological filter - make sure you know what you are getting - make sure to know the SSA.
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