Pond Filtration

What Is Pond Filtration and Why Does It Matter?

A pond filter will help you to get rid of solid waste and harmful ammonia that can build up in your pond. It also keeps the water in your koi pond clear enough to see all of your koi from the top surface. If you do not have a proper filtering system for your koi pond, even the best constructed koi pond will become a health hazard to your koi in days.

An adult koi fish produces at least ten (10) times more waste/biological load than a single adult goldfish; therefore, the filtration system that you select will affect the health of the koi, the clarity of the water, as well as the amount of time you spend cleaning instead of enjoying your pond!

When choosing a koi pond filter system, you should take into account all three types of filtration: mechanical (removal of solid waste), biological (conversion of ammonia to non-harmful nitrate using beneficial bacteria), and UV clarification (removal of free floating algae that cause green water). There is quite a variety of filtration systems available and each one operates differently. The best koi pond filtration system for you is based on the size of your pond, your fish food, and the type of maintenance you would like to do yourself.

Filter Types - Choose What Fits Your Pond

Bead Filters

A bead filter is a type of pressure-filtering system, consisting of thousands of tiny plastic spheres, or beads, that perform both mechanical and biological filtering at the same time. When water flows under pressure through these beads, solids will get trapped in the space between the beads, and beneficial bacteria will attach themselves to the surface of the beads and help to convert ammonia and nitrite into less harmful substances.

Ideal Use: Koi fish that are kept in a lot of water (a.k.a. high-density koi). I've had several koi with a LOT of water and a great deal of demand for high-quality water! Bead filters are designed to manage heavy loads with ease, are easy to backwash and do not require filter media replacement, and are connected in line to the pond return from the pump - which makes them one of the most well-liked types of koi pond filtering devices by dedicated enthusiasts.

Pressurized Filters With UV Clarifier

Using this filter gives you ability to mechanical and biological filtration as well as using ultraviolet (UV) light to kill floating algae cells (green water causes) all in one system. The UV lamp kills floating algae before they have the opportunity to reproduce without chemical treatment while filter media will remove solid material and biological wastes.

Designed for pondkeepers that require clear water without fail! If your pond is in the full sun or has had problems with green water in the past, then a UV-C pressurized filter system is your best choice. Most of these sit outside the pond, just hook up the pump, connect a tube, and let the system do the rest!

Benefits:

• Resolves a green water (single-cell algae) issue
• All-in-one pressurized design and easy to self-install
• Setting up a UV (ultraviolet) source - there is no separate unit to plumb into.
• Ideal for fish owner who wish to maintain a simple setup.

Sizing Correctly: UV wattage (watts) is used to measure the UV output required. It is typically based on your total pond volume and WATER flow through your filter. If the UV system is "undersized", you will not be able to kill algae because the flowrate is greater than what the UV can produce.

Gravity Filters

Gravity filters do not require any external force for filtration; instead, all water flows into the pond using the force of gravity and is passed through various levels of filtration media before being pumped or gravity-flowed back out into the pond. Most gravity filter types have multiple chambers; the first chamber contains sediment and debris that settle to the bottom of the chamber, while the next few chambers progressively separate out smaller particles from the stagnant water by using progressively smaller types of mechanical filter media until all that remains is biological filter media.

Best suited for: Large koi ponds with 3,000+ gallons of water, where a high flow rate may cause stress on the beneficial bacteria in a pressure filter system. Gravity filter systems are the preferred type of koi pond filtration by experienced koi keepers because they are gentle on bacteria colonies and easy to maintain.

Key advantages:

• Capability to handle very high flow rates without dying off of bacteria
• Multi-stage mechanical and biological filtration processes
• Lower operating pressure results in lower energy costs for the pump
• Easy to inspect and clean without having to shut down the filtration system

Gravity filters must be installed at pond level or lower for proper operation, so they are generally installed adjacent to the pond rather than above it.

Waterfall Filters

Waterfall filters (spilling filters and waterfall boxes) filter wastewater from a pond and return them back into the pond through the top of a waterfall. The water is pushed from the bottom of the filter box to the top of the waterfall by a submersible pump where it is filtered by mechanical and biological media before cascading down the edge of the filter box in a manner akin to a waterfall.

Ideal for: Aesthetic ponds with a focus on having a waterfall. These filters are concealed in the back of the waterfall, creating beauty without impeding performance. Aeration occurs in the water as it cascades over each pool, and the filtration system provides both biological and mechanical filtration.

Advantages of Using this Filter:

• Filter is concealed within the waterfall feature.
• Provides both biological and mechanical filtration.
• Aerates water, thus increasing dissolved oxygen content while cascading over an adjacent pool.
• Minimal cleaning effort required, as waste particles are cleansed by gravity.

Typical media included: Matting, lava rock, bio balls, or filter foam depending on the model.

All-in-One Filters

There are different types of pond filters available; this includes an 'All-in-one' pond filter. An 'All-in-one' pond filter contains a water pump, UV clarifier, and multi-stage filtration combined together in one unit, which can either be located inside of the pond (submersible) device or outside of it (above ground). You plug the unit into your electrical outlet, connect the outlet hose to either a fountain head or to a waterfall, and the system manages moving water, UV sterilization, and filtration simultaneously.

For small to medium-sized ponds, water gardens, and beginning setups where simplicity is key, the best choice would be to install your complete filtration unit. If you're going to use your koi pond seasonally and need to install and remove your filter easily, then all-in-one units will also be a good option.

Key features:

• Complete unit replaces 3 separate components: pump, UV, filter.
• Submersible filter designs are virtually undetectable in your pond.
• Only 1 plumbing connection (1 inlet or outlet). Minimal plumbing connections (1 inlet or outlet) required.
• Cost-efficient way to start proper filtration.

It's important to know that an 'all-in-one' filtering system works best with lighter loads of fish in a pond than they do when there is a heavier fish load, such as in the case of a koi pond. In a koi pond, an independent bead or gravity filter will outperform an all-in-one filtering system.

Filtration Kits

A pond filtration kit contains everything needed to set up a complete filtration system: filter unit, a pump to match the flow rates of your filter, UV clarifier (included in some kits), tubing, and all necessary fittings. By purchasing a kit, you'll have eliminated the question of whether or not you have properly lined up the pump's GPH to the filter's capacity.

Who should use a koi pond filtration kit? If you're building a new pond, if this is your first pond, or if you're an experienced pond builder/owner that wants to have a full, complete system with all of your components matched and tested, then a koi pond filtration kit is a perfect choice. Purchasing a complete kit makes it easier to replace items in the future since you know that every part of your filtration system will work together properly.

What typically comes in a koi pond filtration kit?

• Pond filter (pressurized, gravity or all-in-one - type of filter depends on the kit).
• Pump sized to match the filter flow requirement.
• UV clarifier (if included in kit).
• Fits and tubing are needed to attach filter media (being either foam, bio-mass or bead) to the pond filtration kit that you select for your filtration system. Kits vary by pond sizes ranging from 500 gallon garden ponds to 10K+ gallon koi ponds.

Choosing Your Koi Pond Filtration System

Making the wrong choice of filter is the worst and costliest mistake made by pond owners. Using the following simple decision guide will help you make a good choice.

• Determine the volume of your pond. Multiply the length (ft) x width (ft) x average depth (ft) x 7.48 = total gallons.
• Determine how many fish you have in your pond
  • Light: 0-1 inch of fish for 10 gallons of water
  • Moderate: 1-2 inches of fish for 10 gallons of water
  • Heavy: 2+ inch for 10 gallons of water (requires large filter)
• Choose correct filter for your pond

• Filter Size - Make sure to Size UP not down. Filter manufacturers typically rate their filters on idealizing conditions. Actual ponds often have heavier fish loads during summer months and varied feeding rates. It is very common for experienced koi keepers to purchase a filter that is rated to handle 1.5-2x the volume of pond water.

Mechanical vs Biological Filtration - What's the Difference?

The mechanical filtration stage separates solid materials ( fish waste, organic debris, and uneaten food) from the water. This is considered a stage of 'cleaning.' If there is no mechanical filtration, the organic solids decay to ammonia and produce an environment conducive to algae growth.

Beneficial bacteria (primarily Nitrosomonas and Nitrobacter) convert toxic ammonia into two less harmful substances during biological filtration, nitric oxide and nitrate through the nitrogen cycle. Biological filtration is one of the basic building blocks of a successful pond. Each filter in the collection contains filter media such as foam, bio balls, lava rock, and beads that provide a large area for bacteria to colonize.

UV clarification is an additional layer of filtration that destroys any free-floating single-celled algae, bacteria and some parasites by exposing the water to UV light. UV clarification does not replace mechanical or biological filtration; it works in conjunction with both of them. The complete koi pond filtration system incorporates all three stages of filtration; UV filters that are already contained in the pressurized UV units (most all-in-one units and some kits) process all three stages in one unit.

Frequently Asked Questions

What is the best filter system for a koi pond?

When choosing a koi pond filter, keep in mind both the dimensions of the pond and how many fish there will be using it. If your pond holds less than 3,000 gallons, and you only have a normal amount of fish compared to its size, then a pressurized filter with ultraviolet light is probably what you'll want. It combines all three types of filtration (mechanical, biological, and green water) into one device. If you have a large koi pond that is heavily stocked with fish, then you will want to use a gravity-fed multi-chamber filter as it provides the best environment for the bacteria colonies to live and reproduce in since they require low pressure to survive. A bead filter is also a great option for most pond.

How often should I clean my pond filter?

Depending on fish population and temperature, majority of pond filtration systems will require mechanical cleaning (foam rinsing or flushing bead clips) very few times per year (every 2 to 6 weeks). Biological media should not be cleaned using direct tap water. The chlorine present in direct tap water will kill all the nitrobacteria that are essential for the operation of the filter system, therefore, when rinsing biological media you should always use pond water.

Can I use a pressurized filter for a large koi pond?

When appropriately sized, pressurised filters can be used effectively in ponds of approximately 5,000 - 6,000 gallons. Gravity filters are better suited to these larger fish populations because they do not put stress on the bacteria when utilizing higher flow rates. For ponds above 8,000 gallons, a multi-stage gravity filtration system or several bead filters operating in parallel is standard practice.

Do I need a UV clarifier with my pond filter?

Though UV is not an essential piece of equipment for controlling algae in your pond, it is the fastest and most effective means of solving green water issues. In addition to this, UV will eliminate algae cells from your pond before they can multiply, providing clear water to enjoy 24/7. When your pond is exposed to more than six hours of sunlight each day, you will always have algae in your pond regardless of how many aquatic plants, beneficial bacteria, or mechanical filter systems you have in place. Many of the pond filters listed here (e.g., pressurized and all-in-one filters) have UV built into them as a standard feature.

How do I size a pond filter correctly?

Ensure the filter's capacity is at least 1.5 times greater than what is needed for the pond. E.g., a Filter rated for 3,000 gallons would serve well with a 2,000-gallon koi pond. When there is a high fish load, use a filter rated for two times the pond volume. Use a pump to circulate this amount of water through the pond per hour, at least once per hour.

What is the difference between a bead filter and a gravity filter?

A bead filter uses pressure; water is pushed through the filter by your pump. The compact design allows a bead filter to be used in high-density koi ponds where space is at a premium. Because the water flows through a gravity filter due to gravitational force, there is no pressure involved. The more gentle nature of gravity filters is better for keeping beneficial bacteria alive than bead filters, which makes gravity filters a good choice for large ponds where it is important to have stable bacterial colonies. Unlike a bead filter, the gravity-type system must be located at, or below, the pond water level meaning they are generally installed adjacent to the pond instead of above it.

What size pond filter do I need for 1,000 gallons?

For a fish pond that holds 1000 gallons of water and has an average number of fish in it, a filter that can handle a capacity of 1500 to 2000 gallons or so, will be appropriate. Any all-in-one or small pressurized UV filter will typically work well in this type of application. Use a pump rated for 1000 to 1500 GPH or more and expect the total water volume to be processed once within an hour at least.

What filter media works best for koi pond filtration?

The best filter systems use biological filter media that have a large surface area, which allows the maximum amount of bacteria to grow. Bioballs, ceramic rings and K1/K3 Moving Bed Media have all been shown to be excellent for creating large amounts of surface area for bacteria to colonise. For mechanical filtration, open cell foam in progressively finer grades will trap particles without reducing the flow of water to the pump. Most filter systems in this collection are shipped with media already loaded.

Why Proper Pond Filtration Protects Your Investment

Costs of adult koi (from $20-$500+) vary greatly depending upon the variety and quality of each fish you are looking for or purchasing. A 2,000-gallon pond stocked with koi at a reasonable density can yield a value of between $500 - $3,000+ of livestock. If you take proper care of your pond, you'll install a filter system that protects your livestock investment - which costs approximately 10-20% of the value of your fish in one-time costs; therefore, to under-filter your pond could potentially result in larger than average expenses as a pond owner.

Proper filtration also cuts down on interventions to maintain healthy fish in addition to helping to maintain clean ponds, therefore a properly sized and functioning filter should allow averages of approximately thirty minutes per week for pond maintenance compared to two to four hours a week required by undersized or mismatched filters.

Filter Type Descriptions (For Filter Type Collections)

Bead Filters

These are high-quality, specially designed pressurized bead filters to be used in koi ponds. They provide two types of filtration in one single backwashable filter - both mechanical & biological - to meet the high-density koi pond's needs while maintaining a quality water environment without the need for additional equipment or taking up excessive amount of space.

Pressurized Filters with UVC

Pressurized filters with integrated UV clarifiers for pond care. Provides a practical, time-saving solution for keeping your pond clear and healthy while aiding in the promotion of beneficial bacterial growth.

Gravity Filters

Multi-chamber gravity filter functioning at low flow with low damage to beneficial bacterial colonies for extremely high flow rate applications. Recommended for koi keeping with good biological stability in the pond. Comes in sizes ranging from 2,000 to 15,000 gallons or larger +/- depending on use.

Waterfall Filters

Biological filtration is combined with a natural waterfall feature in waterfall filter boxes. The filter is hidden behind the falls, while the water is kept clean and offers aeration for your pond as well! Waterfall filter boxes come in various sizes and flow rates to suit both pump and pond sizes.

All-in-One Filters

You can choose between an external pond filter system and a submersible pond filter system to create your own unique water feature or Koi Pond. Both systems require minimal plumbing because all of their elements (e.g. pump, UV clarifier, multi-stage filtration) are in one compact unit. A pond filtration kit makes building a Koi Pond's filter system easy by including all matched components (pump, filter, UV, and fittings) necessary for the project, eliminating any chances of error from day one.