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The Source for Water Gardening, since 1917


Formulas & Ratios

Liner Size:

Width=widest width of the pond + 2(deepest part of the pond) +2 feet

Length=longest length of the pond + 2(deepest part of the pond) + 2 feet


Think of it this way, the liner needs to get across the widest, longest and deepest part of your pond. Even if your pond is irregular, you need to base your measurements on the widest, longest and deepest portion of your pond. Down and back up the deepest part thus twice the deepest part plus 2 feet which allows for one foot overhang on each side. All measurements must be in feet.


Surface area: length of pond x width of pond, measurements in feet

For this calculation use the average if your pond is irregularly shaped.


Gallons:  length x width x depth x 7.5 = gallons, measurement in feet

Use average measurements if your pond is irregularly shaped.  Err on the lesser side when using additives, especially those for string alage and err on the greater side when choosing a pump.  Over treating for algae may be deadly for your fish and you may always reduce a pump's flow but you can't increase it:)


Stocking ratios

Plants60% surface coverage

Fish: 1 inch of goldfish per 5 gallons of water or 25 gallons of water per one 5 inch fish

         1 inch of koi per 10 gallons of water or 50 gallons of water per one 5 inch koi

Submerged Plants: Using as a filter for your pond, 1 bunch of plants per square foot of surface area. If using as a supplement to appropriate filtration system, one bunch per 5 square feet of surface area.

Scavengers: One per 5 square feet of surface area

Average square footage of surface area:

Waterlily: 10 square feet of surface area

Bog Plant:  2 square feet of surface area

Lotus:  4 square feet of surface area


Pumps:  Pumps are rated by how many gallons they pump at a given vertical lift.  For every 10 feet the water moves horizontally is equal to approximately 1 foot vertically.  To determine the correct pump for your waterfall you need to determine not only your total gallons of water but also the total vertical lift.  


For example, if your pond is 2 feet deep and you are running your tubing 10 feet horizontally and then 2 feet to the top of your waterfall, that is equivalent to 5 vertical feet. (2 feet depth plus 1 foot(10 feet horizontally) plus 2 feet to the top of the waterfall).  You would want to choose a pump that circulates approximately 50% of your total gallons at 5 vertical feet.


Filters and UV lights have recommended flow rates for optimum use.


If you have any questions or would like us to assist you with your individual situation, we're glad to help!  Please call, 301.874.5133, email: or visit our store. Providing accurate measurements and photos are greatly appreciated and necessary to provide you with accurate advice.