Alfagrog a Perfect Biomedium for Fish Pond Filters

When a Pond Filter is combined with an UVC (ultra violet clarifier) in a fish pond the result is clean clear healthy pond water in which fish grow to their full potential for that particular pond. The filter purifies the water and the UVC clarifies or clears the water by killing suspended algae responsible for making pond water murky.

The secret to cleaning the water in a pond biofilter is to have enough biomedium inside the filter so that large populations of cleansing bacteria can live and thrive on the biomedium surface.

Many types of biomedia are to be found in pond filters the most common of which are a variety of plastic tubes or balls.

By far the best filter medium for any type of static biofilter (in other words almost all pond filters) is ALFAGROG. This is a sintered ceramic material specially formulated for use in fish farming. It has been proven in the most extreme biological filtration processes.

1 Litre of Alfagrog (approx 500gm) is sufficient to purify 1,000 litres of pond water with normal stocking density. If you have a high stocking density then increase the amount to 2 litres per 1000 litres of pond water.

The disadvantage of using plastic items is that a large volume of these is required to create sufficient surface on which the bacteria can grow because the plastic is smooth at the surface and does not have a large specific surface area (ie ratio of area to volume). In practice this means the size of the filter box to hold the biomedium gets significantly larger as the pond volume increases. And of course the bigger the filter box the higher the cost.

The cost and performance of any biofilter can be reduced by using more efficient biomedia types and by far the best low cost biomedium in my experience is the UK product, called Alfagrog..

Alfagrog is a fused ceramic product full of small holes which creates a very large specific surface area (ie area of surface relative to volume of the biomedium). In simple terms this means large colonies of bacteria can be grown on small volumes of biomedia. For example 1 litre of Alfagrog will do the same purification job as 40 litres of plastic tubes or balls. This thus means a very small filter box is all that is needed to create an effective pond filter.

Alfagrog can also be mixed with existing filter biomedia such as plastic tubes to create extra filtration capacity to allow for fish growth or higher fish stocking densities. Just mix the Alfagrog with the other biomedia in use.

SSA (specific surface area) in sq.m. per litre of different pond filter biomedia for a home made pond filter is shown below. A high number is best! If an SSA is 1 then theoretically an SSA of 8 will provide surface to hold 8 times as many bacteria inside a pond filter. The same relationship applies to gallons of biomedia.

Alfagrog 45 to 100 depending on particle size

Ceramic Rings 8

Lava Rock 8

Plastic Foam 2.5

Plastic Coils 1