Why You Should Consider A Combined UV and Pond Filter Of The Pressurized Kind

Last week we did the annual exhibition of our fibreglass water features at the UK's premier garden trade show called GLEE. The show is massive and held every year at the National Exhibition Centre in Birmingham.

I have been going to this show for 11 years and always try to "discover" what's "Top Of The Pops" ..... by this I mean not what is new and revolutionary but what has been adopted by the industry in general and has become something of a standard offering. This is a sure sign of success in the marketplace.

Everybody's Now Got One ...

This year the product that everyone was offering was the pressurized pond filter and UV combined.

The first company to offer this type of filter was Hozelock Cyprio around 5 years ago.

Most pressurized pond filters are basically cylindrical in shape with inlet and outlet pipes close to the tight fitting lid.

As such a pressure filter is essentially a container that can be operated under pressure and inside which is a mechanical filter system, biological medium (pond medium (biomedia)) and an UV lamp. The mechanical filter system is normally open celled foam which doubles as a filtration pond medium (biomedia). The better models also include additional pond medium (biomedia) like Alfagrog or SUPRA as it's called in USA.

The single biggest advantage of a pressurized pond filter is that it can be buried and placed anywhere in the pump circuit (even below the pond level) making hiding much easier than with a box type pond filter.

The first thing you will notice about any pressure pond filter is that it is very compact and immediately begs the question why can a pressure filter be so small yet do the same job as a CONSIDERABLY larger conventional pond filter. Those readers who have been with us for some time will probably know the answer. For the newcomers let me explain ...

The effectiveness of any pond filter has nothing to do with the size of the container. It has much to do with the type of pond medium (biomedia) used and also the effective turbulence produced around the pond medium (biomedia) in the filter itself. You should read my coffee and sugar example to better understand this idea. The higher the turbulence the better is the dissolved oxygen and nitrogen food component placed in the immediate vicinity of the filter bacteria. In this way biofiltration efficiency is increased by an enormous amount.

This means the size of a container can be reduced.

A most important reason allowing the success of the pressure pond filter is the inclusion of an UV lamp which kills water-borne suspended algae. This flocculated algae is then removed in the mechanical filtration section of the pressurized pond filter. If there was no UV lamp then the sponges making up the mechanical filter would block very quickly and create excessive cleaning situations. Bear in mind that most cloudy ponds result from suspended algae and not dirt.

A pressurized pond filter cannot work effectively using a normal pond pump which contains a suction strainer sponge. It is preferable to run a solids handling pump directly through the pressure filter. When flow coming out of the filter falls off it is time to clean the sponges.

In the best models this can be easily and quickly achieved without opening the filter itself .... avoid any unit which requires opening to clean it. The pressure required to drive water through this type of pond filter is higher than required for a normal box type pond filter and this must be taken into account when selecting a suitable pump.

Special situations requiring extra attention

The capacity of a pressure pond filter when related to any pond is also a function of the fish mass inside the pond and not just the volume. The reason is that more fish produce more waste which means the filter will block up faster. In addition the larger the amount of fish mass then the larger must the pump be to keep the efficiency of bacterial nitrification at a high level. Remember as flow drops then operating efficiency also drops. This is an excellent reason for choosing a pressure filter with Alfagrog inside it. This allows high conversion efficiency to be maintained as the flow drops due to sponges blocking.

What this means in practice is that you must be very careful in selecting the right pressure pond filter and pump. If a unit is described as handling a pond of say 1,000 gallons this would only be the case if there were no fish (ie plants only) in the pond. If the same pond had goldfish then the capacity might drop to say 500 gallons and with koi it could drop to 250 gallons ..... see what I mean?

Pressurized Pond Filters In Summary summary

1. Choose a pressure pond filter with extra pond medium (biomedia) inside it (not just foam)

2. Choose the size bearing in mind the stated capacity is normally for pond with plants only so read the instructions carefully

3. Choose a suitable (higher pressure, no sponge) pump

4. Choose a pressure pond filter with easy cleaning mechanism.

Oase, Hozelock and Fish Mate make excellent pressurized pond filters and all offer clear water guarantees.