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I’ve always been told to use lava rock in my waterfall filter, is this the best media to use? | Decorative Ponds & Watergardens Q&A


I’ve always been told to use lava rock in my waterfall filter, is this the best media to use?

I’ve always been told to use lava rock in my waterfall filter, is this the best media to use?
Tara – Bon Temps, LA

Lava rock was a common form of biological filtration media in waterfall boxes as its porous surface provides room for bacteria to reside. While it was popular years ago, pond supply companies have since produced better forms of secondary biological filtration media that are friendlier for both you and the pond itself.

Using lava rock as a source of filtration media has a list of distinctive drawbacks. The first of which is that it can prove to be extremely heavy and cumbersome. It is not exactly easy to lift a bag of rocks out of your pond, especially when it is full of water and debris.
While lava rock is porous and can initially provide a reasonable amount of additional surface area, the coarseness and small opening sizes tend to hold on to passing-by debris, blocking the waterways which greatly diminishes the stone’s performance. Once lava rock is loaded with debris you will have to remove it form your filter box and replace it with new media as it is near impossible to remove the debris from within each rock. For some pond owners this means they would need to replace their lava rock media multiple times each season for optimal performance. Furthermore lava rock tends to be brittle and can leave behind additional dust and debris in your pond.

Biological filtration media like Pond Logic® BioBalls™ filter media provides all of the surface area that your beneficial bacteria desire but implement it into a light-weight cost-effective design. One of the best qualities of secondary filtration media like the BioBalls™ is that you only have to buy them once. Pond Logic® BioBalls™ do not degrade over time and can simply be rinsed out at the end of the season and reused the next. BioBalls™ can placed into a mesh media bag and can be placed right into your waterfall filter box.

Pond Talk: Have you used lava rock as filter media in the past and switched to bio balls or another form of media? Did you notice a difference in filtration performance?

Pond Logic® BioBalls™

2 Responses

  1. I am going to build a biofilter next spring and am gathering some supplies a little at a time. My question is does the biofilter have to be elevated above the pond in order for the water to flow back to the pond? I plan on using the skippy filter design along with a few minor adjusments. Also does the inlet have to be smaller than the outlet? Thanks

    • Hi Teresa,

      The location of the filter system depends on the type of filter. If the filter is not completely sealed where pressure from the pump could build up then the filter will need to be above the level of the pond so the gravity will allow the water to flow through. You will want to push water into the filter at the top and drain the water at the bottom back into the pond to ensure the water is passing through the filter media. A sealed pressurized filter system can be placed anywhere outside the pond. Having the outlet larger then the inlet just ensures that the water is able to easily leave the filter system.

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