The Greener View: Water Garden Gravel: Yes or No?

Jeff Rugg on May 21, 2025

Q: We have a new pond, and the question came up about lining the pond with pea- or quarter-size gravel. My water garden friends say they have done it and taken it out. What is your opinion?

A: There is a great deal of confusion and discussion about gravel in a pond. It helps to know the size and style of pond you want to add the gravel to. Large, deep koi ponds rarely use gravel, since the gravel is hard to clean when it is 6 to 10 feet down at the pond bottom. A simple, shallow water garden that is filled with plants can be easy to maintain.

The benefit of gravel is that it provides a much larger surface area for beneficial bacteria and plants to grow. Without that surface area, a larger filter system is required. Ponds with few fish can get by with smaller filters, but fish grow and filters don't, so more filtration may be required eventually. On the minus side, if the gravel is the wrong kind or in the wrong location, it can make some pond cleaning more difficult.

If you were to use a 2-inch layer of pea gravel to hide the liner, water will not circulate through all the pores between the stones. Instead, a single layer of 2-inch stones will still hide the liner and allow the water to flow around each stone, feeding all the bacteria with nutrient-rich water -- and more importantly, oxygen. I wouldn't bother adding gravel to flat areas deeper than 2 to 3 feet down in the pond. They are not all that visible, and the black liner looks like a shadow at deeper depths where gravel would be harder to clean. A mix of gravel ranging in size (e.g., 1-3 inches) looks more attractive than a bunch of rocks all the same size. Larger gravel stones are better for filtration and are easier to clean.

For planting areas on upper shelves, a thicker layer of gravel can be used. Fluctuating water levels will cause the water and nutrients to flow in and out of this area on a regular basis, helping to keep it clean. You can even make "rock flowerpots" by setting a half circle or full circle of grapefruit- to pumpkin-sized rocks on a shelf and filling up the area with 2-inch gravel. Then, wash off the roots of a plant and install it in the rock pot. It now must get all its nutrients from the pond water, not the soil, competing with the algae for nutrients. Plants set up this way look fairly natural in the pond.

Gravel can be useful in the shallow, flat areas of a pond if the pond is less than 2 feet deep. Larger stones can be used to hide the vertical walls of liner.

There will eventually be a buildup of black organic matter in between the stones in the gravel. It is not harmful to fish, since natural ponds are organic matter-filled, clay-lined mud holes. In fact, the Japanese put their most highly prized fish into mud bottom ponds every summer, so they can grow larger and with better coloring than the fish living in the more sterile ponds with no gravel.

If you want to clean out the debris accumulating in the gravel, take the fish out of the pond, placing them in tubs or a small swimming pool. Cover the containers to prevent the fish from jumping out. Drain the pond. Put a pump in the deepest part of the pond and use a hose with a high-power nozzle or a power washer to rinse the gravel starting at the highest point. Pump the water out as you rinse the gravel. This water is very nutrient-rich and can be used to water the garden or lawn as it is pumped out of the pond.

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Email questions to Jeff Rugg at info@greenerview.com. To find out more about Jeff Rugg and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.