Knowing the volume of a koi pond is crucial for several reasons:

  • Planning and Design: Understanding the volume helps in choosing the right filtration system and the appropriate pump size. A mismatch could result in poor water quality, leading to health problems for the koi and potentially requiring more frequent cleaning and maintenance.
  • Fish Health: The volume of water directly impacts the health of the koi fish. We all want more beautiful living jewels for our pond, but overstocking can lead to poor water quality and sick and unhappy fish. General recommendation is to start with at least 1,000 US gallons in your pond and allow at least 200 US gallons per fish (that, however, very much depends on fish size and filtration).
  • Medication and Treatments: When treating the pond for diseases or parasites, knowing the volume is crucial for determining the appropriate dosage of medication or treatments. Incorrect dosages can harm the fish or be ineffective in controlling the issue.
  • Chemical Balance: Maintaining the right chemical balance in the pond, including pH levels and ammonia/nitrate concentrations, relies on knowing the volume of water. Adding chemicals without considering the volume can throw off the balance, harming the ecosystem within the pond.

The most accurate way to calculate water volume in your pond is to use dissolved salt measurements. This calculation will include water within the plumbing, filtration, and attached water features.



Non-iodized Sodium Chloride (NaCl) pure salt with no additives. This kind of salt is inexpensive and is sold in hardware stores for water softeners. Check the label for 100% NaCl.

Here are a few examples: 

Salt Meter

Salt meter prices ranges from under $30 for an inexpensive salt meter designed for pools and spas to about $80 for Hanna Instruments (Koi Jack recommended).

Click on the examples below for purchasing links.

Pen, Paper, and Tape Mesure

Let's Get to Business!

Step 1

Let's figure out how much salt to add to the pond. Use the tape measure to get approximate average measurements for the length, width, and depth of the pond in feet. Enter the measurements into the calculator below.

Step 2

Measure the pond salinity. Note if your meter is using PPM (parts per million), PPT (parts per thousand), or %. ***Tip: give your salinity meter about a minute to produce an accurate measurement.

Step 3

Write down the amount of salt you will be adding to the pond (from the calculator above) and the pond salinity with the unit of measure from Step 2.

Step 4

Add the amount of salt you calculated in Step 1 to the pond.

Step 5

Wait about 24 hours

Step 6

Measure the pond salinity. Make sure you have your meter set to the same unit of measure as you did in Step 2!  ***Tip: give your salinity meter about a minute to produce an accurate measurement.

Step 7

To use the volume calculator, you need your salinity measurement in PPM.

If your meter is in PPT or percent (%) - Click HERE to convert your two measurements to PPM.

Step 8

Enter your initial pond salinity in PPM, pond salinity after 24 hours, and the amount of salt (in pounds) added into the calculator below.

Koi Club of San Diego is a 501(c)(3) organization, and all monetary donations are tax deductible to the fullest extent allowed by tax laws. Please check with your financial advisor if you have more questions. Tax Identification Number: 33-0355312

Powered by Wild Apricot Membership Software