Pond Terms 101: A Comprehensive Guide

Pond Terms 101: A Comprehensive Guide

Whether you’re a beginner or an experienced pond enthusiast, understanding the terminology used in the pond industry is essential for creating and maintaining a healthy, thriving pond ecosystem. From the different types of filters and pumps to the various species of aquatic plants and fish, there is a lot to learn when it comes to ponds. That’s why we’ve compiled a comprehensive glossary of pond terminology to help you navigate the world of pondkeeping. In this glossary, you’ll find definitions of common pond terms, along with helpful tips and insights to help you make informed decisions for your pond. So whether you’re just starting out or looking to expand your pond knowledge, this glossary is an essential resource for anyone who loves ponds.

Above Ground

Refers to the bottom of the pond being at ground level or above.


A solution that has a pH value of less than 7 (neutral).


The process of increasing the dissolved oxygen in water by agitation or movement of water.

Aeration, pond

The process of exposing pond water to air to increase its oxygen levels. This can be achieved through the use of waterfalls, fountains, and aerator nozzles.

Alga Bloom

A rapid growth of algae in a pond.


Lower forms of plant life that have been in existence for millions of years. They thrive in sunlight, nutrient-rich water, and warmth. Two common types are unicellular algae and Spirogyra -filamentous green alga.


A substance used to kill or inhibit the growth of algae. It must be fish, plant, and filter-safe to be used in a pond.


A term used to describe a substance or solution with a pH level greater than 7, indicating a basic or alkaline nature.


A measure of the ability of water to neutralize an acid. It is the capacity of water to resist a change in pH that would make the water more acidic.


A term used to describe the arrangement of leaves on a stem, where a single leaf is attached to the stem at each node, alternating sides with each leaf.


A toxic compound that can be produced in a pond from the decomposition of organic matter such as fish waste, dead plants or animals, or uneaten food. High levels of ammonia can be lethal to aquatic life and should be kept at zero.


A term used to describe a plant that completes its life cycle in a single growing season, producing seeds that can survive the winter and grow again in the next season.


The part of a flower that contains the pollen, a powdery substance that is necessary for plant reproduction.

Axil or Axis

The angle between the upper side of the stem and a leaf or branch. It is the location where a new shoot or branch may grow from the stem.


Microscopic organisms that can be either beneficial or detrimental to a pond, depending on the type and the conditions of the pond. Beneficial bacteria can help to break down organic matter and keep the water clean and healthy.


The appropriate proportion of plants to maintain a healthy ecosystem in a pond. A balanced pond has a variety of plants that can help to oxygenate the water, control algae growth, and provide habitat for aquatic life.


A material used in a bio-filter to provide a large surface area for beneficial bacteria to grow and adhere to, allowing them to break down organic matter and keep the pond water clean and healthy.


The collection of decaying plant material, dead algae cells, fish food, fish excrement, and other elements that contribute to an increase in nitrites and ammonia levels in the water.


Relating to living organisms and their interactions with their environment.

Biological Filters

Filters that use beneficial bacteria to convert harmful nitrites into useful nitrates and remove algae and debris from the water.


The flat, typically green, part of a leaf that is attached to the stem.

Blanket Weed or String Algae

A type of fibrous green algae that grows rapidly in ponds by utilizing excess nutrients in the water.


A naturally occurring or man-made wetland that is typically acidic and rich in peat.

Brackish water

Water that contains higher salt levels than freshwater, but not as much as seawater.


A specialized leaf, usually found at the base of a flower, that supports or encloses the flower.


A small branch or division of a larger branch.


The use of tiles, pavers, stones, or other materials to create a finished surface on top of a water feature or around a pond.

Cascading Sheet Descent Spillways

A type of water feature where water trickles down a wall, rather than projecting out from it.


The part of a plant cell where photosynthesis takes place.


Referring to a structure that consists of two or more similar parts, such as leaflets that form a compound leaf.


Edging material placed to conceal and protect flexible liner or shell.


The process of neutralizing chlorine or chloramine in treated water.

Dissolved Oxygen

The level of oxygen saturation available in water to sustain pond life.

Duty Cycle

The relationship between the running time and the stationary (off) time of a pond pump, based on one hour.

Dye, colorant

A water additive used to minimize sunlight penetration, reduce algae growth, and increase reflective quality.


Refers to aquatic plants that are normally found above the surface of the water, with stiff or rigid stems.

EPDM liner

A type of liner made from rubber and ethylene-propylene diene monomer.


The process of water loss from a pond through evaporation from the surface, which can increase toxin concentration and lower temperature.


The loss of water from a pond due to both evaporation from the water surface and transpiration from plants in the pond.


Structures that are thread-like or hair-like in appearance.


A unit designed to clean and clear water, with mechanical and biological types used for ponds. Can be located in-pond or external, with gravity or pressure types.

Filter media

Various materials used in filters such as plastic discs, balls, foam, and volcanic rock, which facilitate the growth of beneficial bacteria or capture suspended solids in mechanical filtration.


The process of removing suspended solids or converting organic debris and fish waste to less toxic substances.

Filtration, biological

A type of filtration that uses media with active colonies of nitrifying bacteria to reduce ammonia compounds to nitrate.

Filtration, mechanical

A type of filtration that uses media to physically trap suspended solids for removal.

Filtration, natural

The use of aquatic plants in ponds to absorb nutrients, collect silt, and provide food for pond life.

Filtration, vegetable

The placement of select plants in a container, small pond or waterway before flowing into the pond to aid in natural filtration.

Flexible liners

Materials that are pliable enough to allow custom shaping of the pond.


The process of forming lumps or masses, used in water treatment and filter choices.

Flood suction

A type of pond pump inlet located below water level to allow for free flow of water.


One of the small flowers in an inflorescence, as in a spikelet of grass.

Flow rate

The volume of water to be circulated throughout the pond system, measured in liters per hour (lph).


A decorative structure that issues a flow or jet of water.

Fountain head

A nozzle that creates a jet or stream of water, available in various shapes and patterns.


The process of breaking apart and forming fragments or pieces.

Friction Loss

The pressure required to move water through hoses and fittings, which needs to be considered when selecting a pump for a pond.


A parasitic plant that lacks chlorophyll, leaves, true stems, and roots and reproduces by spores.


A column of water ejected into the air from a pump, often created using fountain heads.


An electrical safety device that interrupts electrical flow to submersed devices such as pumps in the event of a malfunction.

Gravity Feed

A pump inlet located below the water level to allow water to flow freely into it.

Green Water Algae

An excess of algae that causes a dramatic imbalance of the pond's microorganisms, treated with water treatment.


High-density polyethylene, commonly used in pre-formed plastic ponds and other items.


A measure of pumping pressure, with 10 meters head equaling 1 Bar at 20°C.

Head Height

The maximum height to which the pump can lift water vertically, beyond which water ceases to flow.

HPDE liner

High-density polyethylene liner.


A chlorosulfonated polyethylene (CSPE) synthetic rubber.


A rotating device inside a pump used to force water through it, usually attached to a magnet.


Refers to the top of the pond being level with the ground surface.


Low-density polyethylene liner.


The leaf-like part of a compound leaf, which is divided into multiple parts.


A part of a plant's leaf that is divided into lobes.

Low Voltage Pump

A pump that operates at 12V or 24V, usually alternating current (AC), with solar pumps normally operating on direct current (DC).

Marginal area

The outer edge of a pond with varying water depths, generally less than 2 feet.

Marginal Plants

Aquatic plants that live in the shallow areas around the edge of a pond.


The central vein of a leaf.


A less toxic byproduct of nitrification that provides nutrients to plants.

Nitrate (water treatment)

A large macronutrient used by plants for food. Levels over 50mg per litre will encourage algae.


A toxic byproduct of fish excrement and decaying organic material.

Nitrite (water treatment)

Lethal to fish and other pond life. Nitrite poisoning causes fish to gasp at water surface.


Stem area (or joint) from which a leaf or leaves, branch or branches originate.


A pump attachment such as a fountain head that creates various water patterns and assists in aeration of the pond water.


Referring to the arrangement of plant parts, usually leaves; leaves are opposite if they appear two per stem node.

Organisms (water treatment and filters)

An individual form of life, such as a plant, animal, bacterium, protist, or fungus; a body made up of organs, organelles, or other parts that work together to carry on the various processes of life.


To produce oxygen in water.

Oxygenating Plants

Plants that emit oxygen into the pond water during photosynthesis.


An animal or plant that lives in or on another and from which it obtains nourishment.


Stalk bearing the flower or fruit.


Living more than two years.


A laminate made of 12-ply cross-grain polyethylene.


The colorful, showy part of a flower that is part of the corolla.


The stalk that attaches the leaf blade to the stem.


A measure of the acidity or alkalinity of water, with a range of 1-14. The ideal range for pond water is 6.5-8.5.

pH reading

The measurement of the acidity or alkalinity of pond water.


The process in green plants and some organisms where light energy is used to convert carbon dioxide and water into carbohydrates.

Pond aesthetics

The overall appearance and design of the pond, including style, size, shape, and how it fits into its surroundings.

Pond Liner

A membrane material used in freeform pond construction to waterproof the pond cavity.

Pond recirculation

The process of completely turning over the volume of water in a pond every 2-6 hours.

Pond shelves

A design element of excavation that leaves an earthen shelf in the pond.

Pond style

The overall theme, style, size, and shape of a pond in relation to its surroundings.

Pond Vacuum

A device used to remove sludge and debris from the bottom of a pond.

Pond volume

The total number of gallons of water in a pond, calculated by multiplying the length, width, and depth, and then by 7.5.

Ponds - Fibreglass

Pre-formed ponds made to look as natural as possible, available in various shapes and sizes.

Ponds: Rigid

Pre-formed pond units that come in varying shapes and sizes, though flexible pond liners are recommended.

Pre-formed shell liner

A high-density polyethylene and fiberglass liner that comes in a pre-designed shape.

Projecting Sheet Spillway

A spillway design that projects a sheet of water into the pond for decorative effect.


A mechanical device that generates water pressure to circulate pond water for filtration and decorative purposes.


A mechanical device used to move water, which can be installed above ground, in-line or submerged.

Pump Cage

A device that limits the size of solids that can enter a submersible pump.

Pump lift

The gallons of water per hour a pump can move, based on the vertical distance in feet from the pump to the discharge height.

PVC (fish grade)

Polyvinyl chloride material that is safe for fish and used in pond construction.


The area at the top of the stem that holds the flower's organs.


A horizontal underground stem that has nodes for new leaves or stems to branch out, often storing food for the plants.


A specialized leaf that encloses an immature bud.


Solid organic matter, silt, rocks, and decaying plant material that settle at the bottom of a pond.


One of the parts of the calyx that makes up an individual flower, usually green.


A surrounding or enveloping structure that is tubular.

Sheer Descent Spillway

A manifold box design that creates a solid sheet of water projecting out from the wall for decorative effect.

Sheet Descent or Cascading Spillway

A manifold box design that creates an even sheet of water running down the wall.


A device that removes debris such as leaves from the surface of a pond.


Buildup of organic matter and waste products at the bottom of a pond.

Solar Panel

A device that produces electricity from sunlight through photovoltaic action, typically used for solar pumps.


A simple long inflorescence with flowers, as seen in pondweeds or pickerelweed.


A small, sessile flower spike with bracts that is reduced in size, characteristic of grasses and sedges.

Spiral Hose

A reinforced hose that is designed to maintain its shape and minimize friction loss, which can degrade pond pump performance, especially in bends.


A nozzle that produces a solid stream of water.


A structure in which spores are formed.


The pollen-producing part of a flower.


A horizontal runner or specialized stem with long internodes that can root at the nodes to establish new plants, such as tape grass.


Growing underwater; a plant may be totally underwater or have some parts above the water. Stems are usually soft or flaccid.

Tannic water

Water that is the color of weak tea, caused by organic matter.

Test Strip

Strips used to measure the most important levels of water quality, including acidity, hardness, nitrites, and nitrates.


Having sharp teeth along the margins, such as hydrilla or naiad leaves.

Transitional zone

The area bordering the pond, planted to provide a natural appearance.


A fleshy or enlarged stolon, such as hydrilla.


A wintering bud that becomes detached and remains motionless at the bottom.


A high density fabric used under pond liner to protect it from puncture, also called geotextile.

UV sterilizer

A device that passes water through an ultraviolet light to kill algae cells, bacteria, and parasites, but increases bioload.

UV-C or U.V. Clarifier

A unit that uses ultraviolet light from a special lamp to kill algae and other microscopic organisms as water passes through it, thus "sterilizing."


Conducting tubes or channels in a plant that are used to move water, food, and minerals; veins are obvious lines on the surface of leaves.


The amount of water contained in a pond or water feature, usually measured in liters.

Water Lilies

Attractive aquatic flowering plants.

Water treatment

Chemicals and/or natural products used in liquid or granule form to maintain optimum water quality for pond life.


A circular or ring arrangement of three or more structures like leaves (e.g., coontail) or flowers.

Last Modified: April 6, 2023