Fish are a great way to add life to your yard and turn your pond into a hobby. With the fish available, pond fish selection can create an exciting trip to the fish store. Before we buy every fish in the store, we should ask ourselves, how many fish can you really add to a pond?
Once we start adding fish to our ponds, we all want more. You'll want to plan ahead to make sure you pick the fish types best suited for you pond size, climate and environment.
We're going to go over what factors are at play while choosing the amount of fish for your particular pond. It's a fairly straight forward process.
Let's get started!
How Many Fish Can You Add to Your Pond?
Experts recommend that you keep no more than 1 inch of fish per 10 gallons of water. Some experts recommend keeping less (about 1/2" inch per 10 gallons of water). Once you select your fish, you'll want to keep a close eye on water quality to ensure the fish bioload isn't greater than your pond can handle.
Remember, unless you get your fish fully grown, they will grow considerably down the road. Domestic Koi reach up to 15 inches long when fully grown while Japanese Koi grow up to 26 inches. Jumbo Koi can reach a whopping 36+ inches long. Goldfish can grow to 18 inches when fully grown depending on the type of goldfish. You'll want to account for growth when adding fish so you don't have the pain of rehoming your fish down the road.
Calculating the approximate gallons of water in your pond
To know how many fish your pond can handle, you'll need to know how many gallons of water are in your pond. Using this number will help you determine the amount of inches of fish your pond can handle.
Formula to determine the gallons of water in your pond:
Average length (ft) x Average width (ft) x Average Depth (ft) x 7.48 = Total gallons (US)
Divide this total by 10 to see how many inches of fish your pond can handle.
For example: A 4ft x 6ft pond at 2 feet deep would be
4 x 6 x 2 = 48 x 7.48 = 359 / 10 = 35.9 (36) inches of fish. Divide this number by the inches of the fully grown fish. So if Goldfish can grow to 18 inches, it would be 36 / 18 = 2
This means if you have a 4ft x 6ft x 2ft pond, you can have a maximum of 2 goldfish when they're fully grown.
Calculating the approximate gallons of water in you stream
If your pond has a stream, this stream also holds water and may get you another few inches of allowable fish. To calculate how many gallons of water are in your stream, use the following calculation:
Maximum length (ft) x Average width (ft) x 0.25 x 7.48 = Total gallons (US)
Examples of How Many Fish You Can Add Based on Your Pond Size
We don't recommend keeping Koi in smaller ponds. The following numbers are based on the maximum amount of fish you'll want to consider adding. These are general numbers and may not suit your specific circumstances.
Pond Size | Pond Depth - Inches of Fish | Number of Goldfish - 18 in | Number of Domestic Koi - 15 in | Number of Japanese Koi - 26 in | Number of Jumbo Koi - 36 in |
4ft x 6ft | 2 ft - 36in | 2 | 2 | Too small | Too small |
​ | 4 ft - 71in | 4 | 4 | Too small | Too small |
6ft x 8ft | 2 ft - 71in | 4 | 4 | Too small | Too small |
​ | 4ft - 143in | 8 | 9 | Too small | Too small |
8ft x 10ft | 2 ft - 119in | 6 | 8 | 4 | Too small |
​ | 4 ft - 239in | 13 | 16 | 9 | Too small |
12ft x 14ft | 2 ft - 251in | 14 | 16 | 9 | 7 |
​ | 4 ft - 502in | 28 | 33 | 19 | 14 |
14ft x 20ft | 2 ft - 418in | 23 | 28 | 16 | 11 |
​ | 4 ft - 837in | 46 | 55 | 32 | 23 |
20ft x 20ft | 2 ft - 598in | 33 | 40 | 23 | 16 |
​ | 4 ft - 1196in | 66 | 80 | 46 | 33 |
What Happens if I Add Too Many Fish to My Pond?
If you add too many fish to your pond, your water quality will suffer and in-turn the health of your fish will suffer. Often times you will need to do constant maintenance including clean outs and water changes. Your filtration will also need to be able to handle a significant bioload.
Fish waste and food that doesn't get eaten quickly will decompose and cause major water quality issues including Ph issues, imbalanced nitrogen cycle, green pea soup algae, diseased fish and slow growing fish.
We do not recommend over stocking your pond. Your fish will thank you for a pond where they have lots of room to swim around.
What Do I Do if I Already Added too Many Fish to My Pond?
If you have already overloaded your pond, you'll want to act quickly in coming up with a plan to bring the amount of fish in your pond to a proper amount. Some things you can do if you've already overstocked your pond are:
Rehome the fish
Set up a stock tank for the extra fish
Build another pond
Upgrade your current pond to a larger pond
The chances are, if you have a pond, you want fish in your pond. Using this guide will help you determine the proper amount you should consider adding.
Q: Do you overstock your pond? What steps do you take to ensure water quality is in check? | Comment Below
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