The first step in the creation of a healthy and transparent pond is the proper selection of a filtration system. As a new or advanced pond keeper, it is important to know what your choices are.
The right pond pump and filter will ensure the clarity of water and the well-being of the fish. Professionals such as That Pond Guy suggest measuring the size of your pond, the amount and type of fish you want to stock and the geographic location before deciding.
This is a rundown of the finest filter systems in diverse pond arrangements.
1. Determine Your Pond’s Needs
To select a filter, pay attention to the following:
- Pond Volume – Calculate length × width × depth (in meters) × 1000 for litres.
- Fish Stock – More fish (especially koi) require stronger filtration.
- Location – Sunlight exposure and depth affect filtration needs.
- Installation Space – Some filters must be placed above water level.
A filter too small won’t keep up, while an oversized one is unnecessary.
2. Types of Pond Filters
Different filters suit different ponds.
The primary alternatives include the following:
In-Pond Filters
- Best for small ponds (under 1,000 litres).
- Not complicated to set up, simply submerge in water.
- Low maintenance but limited for heavy fish loads.
Ideal for: Wildlife ponds, small goldfish ponds.
Pressurized Filters
- Versatile placement (above or below water level).
- Works well with a pond pump for efficient circulation.
- Often includes UV clarifiers to prevent green water.
Ideal for: Medium ponds, raised ponds.
Flow-Through Filters
- Gravity-fed return for efficient water movement.
- Best for large ponds with high fish loads.
- Requires installation above water level.
Ideal for: Koi ponds, large fish ponds.
Drum Filters (Advanced Option)
- Automated cleaning for minimal maintenance.
- Excellent mechanical filtration for heavy waste.
- Often paired with biological filters.
Ideal for: Koi ponds, swim ponds.
3. Choosing the Right Filter Media
A good filter combines mechanical (removes debris) and biological (breaks down toxins) filtration.
- Sponges/Foam – Captures waste and harbours good bacteria.
- Plastic Bio-Media (K1, Bio Balls) – Maximizes area of surface to grow bacteria.
- Activated Carbon – Aids in water purification but has to be replaced.
- GFO (Phosphate Remover) – Lowers phosphates that cause algae.
To achieve greatest effect, a combination of media is ideal.
4. Do You Need a UV Clarifier?
In case your pond becomes green, a UV clarifier assists by:
- Killing single-celled algae.
- Clearing water for better visibility.
- Reducing harmful pathogens.
Many pressurized filters include built-in UV units.
5. Final Tips for Selection
- Wildlife Ponds – Simple in-pond filters work well.
- Goldfish Ponds – Pressurized or flow-through filters are ideal.
- Koi Ponds – Drum filters + biological media are best.
That Pond Guy recommends that it is always better to get a slightly bigger filter than what is prescribed to accommodate the sudden increase in fish growth or additional waste materials.
Wrapping Up
The most appropriate filter will be determined by the size of your pond, the number of fish in it and its arrangement. Choosing in-pond, pressurized, or drum filter, make sure that it will fit your requirements of having clear and healthy water.
