How many Fish Can I Have in my Pond?

How many fish can I have in my pond

How many Fish Can I Hlave in my Pond                                                                            

To understand what fish need to thrive in your pond, keep in mind that koi can grow to 30 inches long!  If the pond supports this growth they will grow and be healthy.  If not, it will cause stress to the fish and they become vulnerable to illnesses and infection.  Essentially, a pond needs roughly 10 gallons of water to live in for each inch of their length.  So – one  6-inch fish needs 60 gallons of water.  However, they actually need more than that because they need to grow. 

If you had a 8 x 10 rounded pond that was about 2 feet deep, it would hold roughly 1,184 gallons of water.  If you had 10 6-inch fish we know that they need at least 600 gallons.  So 1,184 gallons would be plenty and leave them room to grow.  If they made more fish (happy fish often do this!) you might suddenly have 10 6-inch fish and 20 2-inch fish.   As they grow you would need to “cull” your fish.  To cut down on the number of fish, remove some fish to give enough water for fish to be comfortable and grow.  Eventually through culling each year as necessary, your fish could grow to 30 inches (remember they need 300 gallons of water each).  This means that your 8 x 10 pond may have only 3 or 4 fish that are 30 inches long.

You always have the option of culling the larger fish and keeping the small ones if you want more fish.  OR – call us and we can expand your pond!

Overstocking fish creates an imbalance in the pond’s ecosystem and can be detrimental to the health of your fish.  Goldfish can be kept in closer proximity.

This table is a general guide for fish about 7 inches long.  This also assumes good conditions regarding circulation, aeration, filtration, bacteria colonization and good plant life.

How many Fish Can I Have in my Pond?

Pond size (assuming a rounded shape at 2 ft deep) # gold fish or # Koi
5 x 5 7 4
5 x 8 12 7
8 x 10 21 13
10 x 10 25 16
12 x 10 30 19

Want to understand the numbers?  Using the equation to figure out the gallons of your pond, you can figure out how many fish you can have.  (L x W x 80%) x average depth x 7.48 = gallons in a pond.  We use 80%  here, because ponds are not square; they are about 80% of a square.  So if you have a 10 x 8 foot pond with an average depth of 2 feet, it would look like this: 10 x 8 x .80 = 64.   64 x 2 x 7.48= 957.44 gallons.  957.44 divided by 74.8 (assuming a 7 inch koi) = 12.8.   I would round up to 13 (no one wants to see 80% of a fish!)

Want more information on how to keep a pond healthy?  Click HERE for more fish care basics.