Discover the Best Plants for Natural Pond Filtration

The establishment of a thriving pond requires more than clear water because it depends on the perfect harmony between fish and plants and beneficial bacteria populations.

While lake water treatments often focus on chemicals, a well-designed biological filtration system offers a natural, sustainable solution. The That Pond Guy team, which serves as a pond expert centre, recognizes biological filtration knowledge as essential for developing effective, low-maintenance pond systems.

How Biological Filtration Works

Biological filtration depends on helpful bacteria that transform dangerous substances such as ammonia and nitrites into less toxic nitrates. Bacteria select filter media along with rocks and gravel to act as natural waste recyclers. When beneficial bacteria are absent, the pond becomes toxic due to undigested fish waste and decomposing organic materials.

Artificial water purification follows the natural procedure where bacteria join forces with plants to clean water. Man-made ponds need the assistance of proper filter systems to support the natural water purification process.

Types of Biological Filters

Not all filters are created equal.

Here are the most common types:

Submerged Filters: The bacteria survive underwater through access to oxygen-rich water.
Trickle Filters: The flowing water enhances media oxygenation, which supports bacterial reproduction.
Moving-Bed Reactors: Use floating media for efficient mixing and biofilm development.
Fluidized Sand Filters: These systems handle large waste quantities yet need continuous operation.

A submerged or trickle filter suits most garden ponds yet koi ponds require moving-bed reactors for proper filtration.

Choosing the Right Filter for Your Pond

Size matters! A filter too small will not keep up with waste, while an oversized one wastes energy.

Follow these guidelines:

Small ponds (under 1,000 litres): Compact biofilters with sponge media.
Medium ponds (1,000–5,000 litres): Multi-chamber filtration systems consist of mechanical and biological processing units.
Large ponds (5,000+ litres) or koi ponds: High-capacity filtration systems include bead filters or moving beds.

Pro Tip: Always oversize slightly—fish grow, and waste increases over time!

Boosting Filtration with Plants and UV

Aquatic plants are nature’s purifiers, absorbing excess nitrates and shading out algae. Pair them with a UV clarifier to zap free-floating algae and keep water crystal clear.

Just remember:

UV lights do not replace biological filters—they complement them.
Clean the UV sleeve regularly and replace bulbs annually for peak performance.

Maintenance Tips for a Healthy System

Avoid tap water for cleaning: It kills beneficial bacteria. Use pond water instead.
Clean media in stages: Never scrub all filter media at once; preserve bacterial colonies.
Test water regularly: Ammonia, nitrites, and pH should be checked monthly.
Run filters year-round: Shut them down only if the pond freezes.

Troubleshooting Common Issues

Green water? Check UV function and reduce feeding.
Ammonia spikes? Add bacterial supplements and ensure proper aeration.
Clogged filters? Clean mechanical pre-filters weekly during peak season.

Final Thoughts

Biological filtration systems are essential for keeping a pond healthy. Mimicking natural cycles leads to clear water alongside content fish with reduced chemical needs. For expert advice, That Pond Guy offers tailored solutions to keep your pond in perfect balance.