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General Pond Questions

When calculating your fish load, think of it in pounds of fish or total inches. For example, one 6” fish can weigh as much as four 4” fish. The number of fish will affect the overall fish load. Although 10 small fish may only produce the waste of one large fish. With this said, remember that your fish are growing and in many cases multiplying. Always plan for the future and be careful not to overstock your pond.

The size and type of your filtration system will depend on your total fish load. If your filter is not properly sized for maximum potential, your fish will outgrow the filter. In most cases filters on the market are rated for ponds containing no fish or a minimal fish load. It is always best to get a filter that is rated for at least 2x the water volume of your pond.

A rule of thumb is to have 60% plant coverage. This should consist of submerged, floating and marginal plants. Floating plants pull their nutrients directly from the water. Rooted plants and marginal plants, create a great place for your fish to hide from predators. Please note when aquatic plants are not present, algae will take their place.

Auto-Fill Valves or Water Level Controllers

Auto-Fill valves or Water Level Controllers are a convenient way to control the water level in any pond or water feature. They ensure that there is always a sufficient amount of water in your pond or water feature to prevent the pump from running dry and burning out.

Technical Questions and Calculations

One cubic foot of water = 7.48 gallons. (7.5 is often used for easier calcualtions).

To find the gallons of water in a pond multiply the width x length x average depth x 7.5

For example: A pond is 15 x 20 x 3 ft deep x 7.5. There are 6750 gallons of water in the pond.

Light Flow = 100 gph per inch of spillway

Average Flow = 150 gph per inch of spillway

High Flow = 200 gph per inch of spillway

Width of Spillway x Desired Flow Rate = Total GPH

Examples for waterfalls with a 24” wide spillway:

Light Flow: 24” Spillway x 100 GPH = 2,400 gph

Average Flow: 24” Spillway x 150 GPH = 3,600 gph

High Flow: 24” Spillway x 200 GPH = 4,800 gph

  1. Calculate waterfall flow rate
  2. Determine length of hose needed
  3. Determine height of waterfall
  4. Determine number of elbow hose fittings

Add 1 ft of head for every 10 ft of hose

Add 1 ft of head for every elbow fitting

Example of a 24” wide waterfall that requires 3,600 gph and is 5ft above the pond and has 20 ft of hose and 2 elbow fittings:

Waterfall height + Hose+ Fittings = Total Pump Head

5 ft + 2 ft + 2 ft = 9 feet of head

You will need a pump that provides 3,600 gph at 9ft of head.

A good rule of thumb for waterfall reservoirs is to make the reservoir 2 to 3 times the volume of the total water in the stream or waterfall.

Example of a 3 ft wide stream that is 30 ft long and has a average depth of 3”.

3 x 30 x .25 x 7.5 = 168.75 gallons Recommended reservoir size is 350 to 500 gallons.

Pump Head is calculated by measuring how many feet the water will drop from the top of the waterfall to the water’s surface. Also, add one foot of head for every 10’ tubing.

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