Are Rocks and Gravel Safe for A Pond?
If you have been researching different types of ponds for any length of time it’s very likely that you’ve run across a heated debate between the “rocks and gravel are cool” and the “rocks and gravel will kill us all” groups. It is a debate that can be seen raging on forums and articles across the web.
On one side you will find the group who argue that having rocks and gravel on the bottom of a pond will kill all the fish and cause poor water quality.
The other side says that rocks and gravel are fine and in fact will help house good bacteria to break down organic waste that collects on the bottom as well as create a natural aquascape.
So, who’s right? The answer is, it depends on what you are looking for.
Liner bottom pond
Pro:
- Easier to vacuum on a daily or weekly basis
- Best used with a UV light in order to kill all naturally existing bacteria, both the beneficial and destructive
Con:
- Creates an unnatural looking pond, like an outdoor aquarium
- Any debris that falls to the bottom is not consumed by heterotrophic (beneficial) bacteria where it accumulates and needs to be addressed.
Gravel bottom pond
Pro:
- Natural look and feel, like Mother nature built it herself
- When balanced correctly with plants, fish, and filtration, it is very low maintenance with no vacuuming required
- Offers large areas for beneficial bacteria to thrive
Con:
- Like any pond, if it is left to sit without maintenance for years on end it may become too toxic for fish life
- The build cost is higher due to the cost of rocks and gravel
From our extensive research and experience with the issue we’ve found that it really comes down to a matter of personal preference. If you are looking for a water feature that can provide the absolute healthiest environment for your prize Koi then perhaps a bare liner pond is exactly what you need. It will allow you to vacuum the pond on a weekly basis and have as much control over the amount of organic compounds in the pond as possible.
The smooth liner surface does not have the high surface area for bacteria colonization that gravel does, but it allows for easier vacuuming. A liner bottom pond can be thought of as an outdoor aquarium where the chemical properties of the pond can be stringently monitored and controlled to ensure that delicate fish species can be cared for to the enth degree.
We have found, when built and maintained correctly, a natural ecosystem pond that includes gravel and rocks is in no way unhealthy for fish. We have many customers who have gravel and rocks in their ponds along with some great looking Koi and other fish, and the fish have been doing very well for many years.
The use of rocks and gravel in the pond creates a large surface area for heterotrophic (beneficial) bacteria to colonize. To provide this surface area, we like to use gravel that is one inch to three inches in size. This beneficial bacteria thrives by consuming decomposing organic materials which helps naturally get rid of organic waste in the pond.
Heterotrophic bacteria is an aerobic bacteria which means it requires oxygenated water. Having good water circulation throughout the pond depths, submerged oxygenating plants, or using an aerator will fulfill this need. A cleanout of the pond, detailed here, performed every year or every few years will keep the pond looking pristine with an ecosystem that’s in balance.
Another benefit to covering up the liner with rocks and gravel also helps to protect your liner from UV light degradation and extends the lifetime of the liner membrane.
Ponds require maintenance regardless of the type. So, if you have some prize fish that are extremely expensive and mean the world to you, a bare liner pond may be the best option, but you might also be putting more time and/or money into it.
A pond that has gravel and rocks instead of a bare liner, when done correctly, should look like mother nature built it herself. These ponds, ecosystem ponds, rely on the balance between plants, fish, bacteria, and filtration to stay healthy and beautiful, and it works!
Having a beautiful natural looking ecosystem pond in your backyard will create a relaxing paradise where you can unwind and enjoy the pond life.
