Why A Bead filter is a Good Choice For Larger Koi and Gold Fish Ponds

A Bead filter for koi ponds

Based upon chemical engineering principles alone a bead filter should be one of the very best types of biofilter especially for larger koi ponds. However I have no personal practical experience of a bead filter often called a fluidised bed biofilter.

Despite this let me explain why a bead filter should be so good.

First though a bead filter is probably overkill in most small to medium garden ponds. Take a look at some here by clicking the link. A bead filter should be used for larger garden ponds and koi ponds requiring extra special filtration.

If you refer back to my coffee cup description of biofiltration then a bead filter is a continuously stirred coffee cup. What sort of pond filter could be better?

In a bead filter (shorter more descriptive name for fluidised bed filter) beads are actually suspended in a turbulent mass of water. The beads are being thrashed about and are always in contact with fresh water and oxygen and ammonia. The bacteria in the bead filter are actually sitting on the bead surfaces. They  convert ammonia to nitrite then to nitrate very quickly indeed.

In some types of bead filter there are up to 600,000 beads per cubic foot of filter space this is very high surface area, just like we discussed earlier.

Rule of thumb sizing for a bead filter is as follows

1 cubic foot of beads can convert the ammonia released from 1 lb of 35% protein fish food daily. This can be translated as 1 cubic foot of beads will look after a pond containing 100 lbs of fish.

Solids accumulate on the biofilm of the beads in the fluidised bead filter and are removed by backwashing the bead filter.

A word of warning about this type of filter . Very small or broken beads can actually block what are called laterals inside the filter. It must be possible to remove these laterals for cleaning out if necessary.