Bead Pond Filters. To bead or not to bead?

Bead filters represent a departure from ‘traditional’ pond filtration. How are they different, what do they offer and could you or your fish benefit from bead filtration?

Pond keeping, especially if it involves koi can be an expensive business. As more of us focus our creativity to the garden, turning it into the outside room of our house, we of course want it to look as good as the rest of our home and invest in it accordingly. As no garden can be complete without a pond, and no pond complete without fish, without really noticing, our attentions can become divided between the décor of our garden and the health and welfare of our fish.

Recognising that maintaining a healthy pond environment is the secret behind keeping fish in good condition and that a suitable filter system lies at the heart of that secret, it makes sense for us to spend time investigating what you, your pond and your fish may require from a filter. A pond filter will wear many different hats, performing a combination of complementary functions to maintain a healthy pond. These will include solids removal, biological action for the bacterial breakdown of waste as well as being user-friendly in the space it requires and time it demands for maintenance.

In fact, the majority of pond owners, when choosing a filter, strike a balance between filter efficiency and performance and its maintenance needs (ie how often you have to roll your sleeves up to work on the filter). If maintenance was not an issue, then we would choose ultra-fine pore filtration systems that intercept the finest of particles, but would need cleaning or backwashing on a daily basis. Well I thought pond keeping was a leisure activity!

The industry standard, found in most ponds, will generally include a chamber (single unit filter box) or a series of chambers that will perform the vital roles of a filter, effectively but not too efficiently in that they will not require regular time-consuming maintenance. Nevertheless, such systems (consisting of an array of filter media such as brushes, foams and grades of other inert media) have provided us with excellent pond conditions for many generations.

More recently, the ornamental pond and koi sector has been introduced to a form of filtration that is new to the back yard, having successfully served it’s time in numerous commercial aquaculture applications around the world. A new family of filters has emerged under the descriptive name of ‘bead filters’ which relates to the type of media employed by these units. They are certainly unique in their operation (and sometimes their appearance) and offer an alternative to the standard forms of chambered (either single or multi) filtration that are more commonly used in garden ponds.

Having had a good deal of experience in recirculating systems in commercial aquaculture, I have regularly been introduced to the latest filtration innovations in a bid to see me upgrade existing successful and efficient systems. To the salesmen’s frustration, they were usually met with the measured response, ‘if it isn’t broken, why fix it?’.

We could justifiably respond to the advent of bead filters in pond keeping in the same way. Yet bead filters have earned their keep in commercial aquaculture (which is no mean feat) and can we, as pond owners, benefit from their innovative approach to filtration, whether considering them for a new or existing pond?

What are bead filters?

Bead filters are completely enclosed vessels through which water is pumped. Within the vessel (which may be shaped like a standard sand pressure filter through to a Darlek-esque hour-glass structure) thousands of beads are retained where they perform their filtering role. The two different shapes account for the two ways bead filters can be operated and cleaned.

What are the beads and what do they do?

The beads (from which these filters get their name) are the ‘business end’ of the filter and are made from a buoyant polyethylene plastic, each of which is 1/8” in diameter.. They achieve both mechanical (solid entrapment) and biological (bacterial breakdown of waste) functions in a similar way to an undergravel filter that has been turned on its head. Where gravel in an undergravel filter serves both mechanical and biological functions on the base of an aquarium, the buoyant beads do exactly the same but in the top of the filter. That is where the similarity ends, as typically, a bead filter is cleaned more frequently (on a weekly basis) where as an undergravel filter could be cleaned once every 3 months!

The beads supply a large surface area (but are not porous, unlike other biological media) attracting a film of bacterial growth within the steady stream of pond water. As the beads accumulate and ‘bed down’ at the apex of the filter, they also form an effective mechanical filter, screening the water of particulate matter down to 20 microns. Finer particles (less than 20 microns) can also become trapped in the sticky bacterial film that coats each bead.

Eventually, the floating bed of the multi-functional beads will become blocked with the debris that they have been designed to intercept. Evidence of this will be a drop in the through put of water through the filter (particularly visible if the bubblebead filter outlet feeds a waterfall) or on the pressurised bead filters, a similar drop in turnover coupled with the reading from the integral pressure gauge.

Cleaning involves a backwashing process which will very between models.

a. Bubblebead Filters. In these ‘hourglass’ units, the inlet is closed and an adjacent backwash valve at the bottom is opened. Air is also introduced into the lower chamber just beneath the constriction to relieve the vacuum within the vessel, allowing the water and bead bed to drop under their own weight , down through the constriction, breaking up and agitating the bed of accumulated debris and beads as it goes. The discharged nutrient-rich water is diverted onto the garden or down a drain while the perforated pipework within the chamber retains all of the beads in the filter. The discharge valve is closed and the pumped water reintroduced from the pond to re-float the beads. Unless backwashing is 100% efficient, there can be a tendency for cloudy water to re-enter the pond from the filter, but this will soon be trapped the next time it comes into contact with the bead bed.

Some models of bubblebead filters are fitted with pressure sensitive valving which means that when the pump is turned off, the filter drains and backwashes automatically through the discharge valve. To take full advantage of this, a simple timer can be installed to cut the power to the pump for 15 minutes each day, thereby backwashing your filter automatically each day. You will need to install an auto top-up system to maintain the water level in the pond, thus making backwashing a completely automatic process.

b. Fully pressurised bead filters take their technology from a sand pressure filter, with redesigned internal pipework.  As with the bubble bead, the water is introduced through perforated pipework at the bottom and leaves the filter through a perforated pipe at the top, adjacent to the floating bead bed.  During back wash, the ingenious multi-port valve control (again – borrowed from the swimming pool domain) is turned to ‘back wash’ where, under pressure, the bed and debris are agitated and the particulate matter discharged.  Before putting the filter back on line, it is put through a pumped rinse, ensuring that no debris at all is reintroduced to the pond.  Due to the higher pressures utilised in a bead filter, smaller beads can be used which can result in more finely polished water.

Siting and Installation

Most bead filters are used to complement existing filtration, where conventional mechanical filtration (vortex, brushes or settlement chamber that are best fed by a bottom drain), removes the worst of the particulate matter, for the bead filter to ‘polish’ and carry out the biological function.  Both types of bead filter are pump-fed.

Even though the ‘foot print’ of bead filters is relatively small, some can prove a challenge when location them aesthetically.  Bubblebead filters really need to be sited above ground and water level so they can be drained efficiently (unless there is direct access to a below ground drain).  As some units are 7 feet high, this can make concealing them challenging, with pond owners opting to install them in a shed or garage, which is fine so long as the pumping, pipework and drainage arrangements are adequate.

The fully pressurised bead filter (adapted swimming pool filter), can be run in a below-ground chamber quite adequately, as long as the discharge pipe has access to a proper drain, as the volume discharged during a backwash can be considerably more than a bubble–bead filter.

What size of filter for what size pond?

As most bead filters work in conjunction with another means of mechanical filtration prior to the bead filter, the factor that determines the size of the filter is largely the quantity of fish (and hence food) that the pond experiences.  The biological action is determined by the surface areas (number of beads) which in turn is governed by the volume of the bead filter.

Bead filters:                           Pond Volume (gals) up to (Average Stock rate):

1.75 cubic foot                       2,500

2.5 cubic foot                         5,000

4.25 cubic foot                       10.000

6.0 cubic foot                         15,000

9.0 cubic foot                         25,000

Bead filters can be used as stand alone units, without any supplementary mechanical filtration, but this can cause them to clog very frequently, requiring regular backwashing.  Clogging occurs at an even faster rate when used in conjunction with a UV clarifier on account of the excessive levels of glutinous algae residue that is produced.

So why change over to bead filtration?

This is the question I would ask, especially if I am happy with my existing filtration.  However, if you are looking at a new pond project, are tight for space (or time) and like the idea of an automatic, hands-free backwash system that looks after itself, coupled with enhanced biological activity that means you can get away with the odd case of over indulgence (over feeding!) then a bead filter may just be what you and your pond fish require.

Kill blanketweed and string algae.