How many fish can I have in my pond?How Many Fish
Will Your Pond's Filtration System Support?

Here's how to calculate EXACTLY how many fish you can have in your pond.  You need to know the following:


  • The SSA of your biological filter (Calculate SSA of media inside the biofilter)
  • The type of pond - rock & gravel pond without bottom drains, or smooth lined ponds with pre-filtered bottom drains
  • The SSA of all surfaces in your pond including waterfalls and streams (Rock and gravel SSA calculations)
  • The volume of water in the system
  • Dissolved oxygen is above 5 mg/l
  • Total water volume re-circulated through the biofiltration system a minimum of once every 3 hours

Rock & Gravel ponds with skimmers and biofilters only process fish waste along with processing ammonia.  For Rock & Gravel ponds use the Total Fish Waste the pond and filter can process to find the Total Fish by Weight that pond can effectively maintain.

Smooth lined ponds with skimmers, biofilters, and pre-filtered bottom drains remove all waste prior to biologic stage - so the biofilters process ammonia and dissolved organics only. For completely pre-filtered smooth lined ponds use the Total Ammonia to find the Total Fish by Weight that pond can effectively maintain.

Rock & Gravel Pond Example:

A 14' x 16' foot pond with a maximum depth of 4' lined with 18" - 24" granite boulders on the vertical sides and 3/8" pea gravel on the horizontal surfaces with a 9' x 2' stream.  The water meter measured water volume is 2,280 gallons.  The biofilter has a Total SSA of 1,354.  The pump is 4,700 gallons per hour. Bottom aeration and waterfalls keep the dissolved oxygen levels well above 5 mg/l in temperatures above 85°.  How many fish can you place in this pond?

Here's how to figure it out......exactly, with mathematics. 

Biological filter's SSA is 1,354 (Calculate SSA of media inside the biofilter)

Pond's SSA 3,792 (Rock and gravel SSA calculations)

Horizontal Surfaces:
14'w x 16'l x 12 SSA = 2,688 SSA

Vertical Surfaces:
14'w x 4'h x 2 sides x 4 SSA = 448 SSA
16'l x 4'h x 2 sides x 4 SSA = 512 SSA

9'l x 2'w x 8 SSA = 144 SSA
(2,688 + 448 + 512 + 144 = 3,792)

TSSA = 5,146

5,146 x .2 = 1,029.20 grams of fish waste.
1,029.20 x 3 = 3,087.60 grams of fish weight produced the waste.

Water volume is 2,280 gallons.

Multiply 3,087.60 Fish Weight by 1.228 (The 1,000 Gallon Factor)

3,791.57 Total Grams of Fish Weight can live in this pond.

Go to Fish Weights determine what sizes of fish this translates into.

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