Filtering a pond involves creating a balanced ecosystem that naturally cleans the water. This primarily involves utilizing plants and beneficial bacteria. Aim to cover roughly two-thirds of the pond's surface area with plants to achieve a naturally clear and healthy pond.
Here's a breakdown of the process:
1. Utilizing Plants for Natural Filtration:
- The Principle: Plants absorb nutrients and toxins (like nitrates and phosphates) produced by fish waste and decaying organic matter. This prevents algae blooms and clarifies the water.
- Types of Plants:
- Submerged Plants (Oxygenators): These plants live entirely underwater and release oxygen, which is vital for fish and beneficial bacteria. Examples include anacharis (Elodea), hornwort, and coontail.
- Floating Plants: These plants, like water lilies and water hyacinths, provide shade, which helps to control algae growth by limiting sunlight. They also absorb nutrients directly from the water. Be cautious with invasive species like water hyacinth, as they can rapidly overpopulate.
- Marginal Plants: These plants grow around the edges of the pond and filter runoff before it enters the main body of water. Examples include irises, cattails, and marsh marigolds.
- Plant Coverage: As stated previously, approximately two-thirds of the pond surface should be covered with plants.
2. Beneficial Bacteria:
- The Role of Bacteria: Beneficial bacteria colonize surfaces within the pond (rocks, plant roots, filter media). They break down organic waste (fish waste, decaying leaves) and convert harmful substances like ammonia and nitrites into less toxic nitrates. Plants then absorb these nitrates.
- How to Encourage Beneficial Bacteria:
- Surface Area: Provide plenty of surface area for bacteria to colonize. This can be achieved through rocks, gravel, and specialized filter media.
- Oxygen: Ensure adequate oxygen levels in the pond, as beneficial bacteria are aerobic. This can be achieved through plant life and, if necessary, a small fountain or aerator.
- Avoid Over-Cleaning: Don't completely drain and clean the pond frequently, as this will kill the beneficial bacteria colonies.
3. Combining Plants and Bacteria:
The key is to combine a good plant population with enough surface area and oxygen for the beneficial bacteria to thrive. Together, they create a natural filtration system that keeps the pond clean and healthy.
4. Additional Tips for a Clear Pond:
- Avoid Overfeeding Fish: Excess food will contribute to higher levels of waste and algae growth.
- Regularly Remove Debris: Remove fallen leaves and other debris to prevent decomposition and the release of excess nutrients.
- Consider a Mechanical Filter (Optional): While plants and bacteria are the core of natural filtration, a mechanical filter (like a skimmer) can help remove larger debris before it decomposes.
- UV Clarifier (Optional): A UV clarifier can help control algae blooms by killing algae cells. This is generally used as a supplement to natural filtration, not a replacement.
In summary, filtering a pond naturally requires a balance of aquatic plants to absorb nutrients and beneficial bacteria to break down waste. Proper maintenance and avoidance of overfeeding will also contribute to a clear and healthy pond environment.
