Here we see the stones after having been rinsed and all floating
debris being poured off. The good bacteria remain on the
stones - no need to disturb these by excessive cleaning. If
and when a particular tub/problem develops the filters are laid out
in the sun and dried out completely - allowing the ultra-violet rays
of the sun to thoroughly kill off any residual bacteria or
micro-organisms.
Cleaned/washed/rinsed stones being poured round and on top of the
plastic filter. These stones were obtained from the Linthipe
river many years ago - they are not too fine and do not
"pack" too closely. The key factor is that of water
movement through the stones - and smaller/finer sand (we have tried
this) clogs very rapidly and is not successful.
This photo shows a somewhat dirty filter that needs
cleaning. Basins are made locally - in Malawi - and
filters are obtained with difficulty from South
Africa. The white centre pipe carries air to all of
the concrete tubs - the black piping supplies the water - pumped
from two 86,000 litre reservoirs which are filled from the
lake.
Back goes the filter after cleaning. Every 60 days a
full tub-cleaning exercise is carried out - based on a review of the
general condition. All water is drained (after fish removal) and
after a vigorous scrub-down of the tub it is filled with fresh water
from the reservoirs. Food is normally a good quality flake
food from a South African fish food supplier.
