Gardena 7904 Operating Instructions Manual - page 4
17
G
16
G
➔Multi-layer biological filter system with a very large surface area
Here pollutants are decomposed using oxygen (aerobic process)
and without oxygen (anaerobic process). Harmful nitrites are
decomposed by useful bacteria, which become established in the
system.
The previously purified pond water is subjected to radiation with
short-wave UVC light (ultraviolet radiation). This reduces growth
of algae and fights harmful bacteria which may cause diseases
in fish.
70 mm standard outlet connection for, e.g., soil pipes.
Drain for sludge and water. Prior to frosty conditions, for example,
the filter can be drained and may be left outside during winter.
To indicate the UVC light is switched on (blue lamp).
* applies only to GARDENA Pond Filter with UVC light, Art. No. 7905
The UVC-light for the Pond Filter Art. No. 7904 is available from GARDENA Customer Services.
$
Biological purification
of the water
%
*
UVC-radiation
&
Connection for
sewage pipes
/
Water and
dirt-drain screw
(
Inspection glass
Function
.
May be connected to the connection hose leading to the pump
in the pond.
.
The water flows into the filter forming a circle. The water de-
flector (= inlet nozzle) causes powerful swirling movements in
the water, supplying it with oxygen from the air.
Floating substances and biological sludge form deposits due to
centrifugal force and the effects of gravity.
➔ Coarse mechanical filtering (black filter foam)
Large dirt particles are retained by the high-volume foam filter
element. The concentration of oxygen causes the formation of
nitrosomonas bacteria, which transform ammonia, a substance
highly harmful to fish, into nitrite.
➔ Fine mechanical filtering and biological filtering (grey foam filter)
With the help of oxygen and nitrobacter-bacteria, nitrites are
decomposed into nitrates. Nitrates can be absorbed naturally by
plants and decomposed.
Pos. Element
!
Water inlet
"
Vortex-System
(Deposit area)
§
Mechanical
multi-filtering
Operation
The universal fitting provides various options for fitting a hose,
i.e., connections for
.
19 mm (3 /4”) or
.
25 mm (1”) or
.
32 mm (1 1/ 4 ”) or
.
38 mm (1 1/ 2 ”) hoses.
➔ Using a saw, cut off the parts of the universal fitting that you do
not need inside the nut, otherwise the pump may perform less
efficiently.
➔ To choose a hose size, please read paragraph “Installation
Instructions”.
Push 2 hose-clips over the ends of the hose, then push the hose
into the universal fitting and over the pump connection. Fix the
hose using these hose-clips. If necessary, assemble the universal
fitting and water deflector after dismantling
If you have unscrewed the universal fitting in order to saw part
of it off, assemble it as follows :
.
Remove the cover of your pond filter.
.
Using one hand, hold the water deflector (= inlet nozzle) with
the opening pointing downwards, on the inside of the pond filter,
and with the other hand, firmly screw on the universal fitting
from the outside.
➔ Make sure the seal is properly fitted.
.
Adjust the water deflector to an angle of 15 - 30° to the vertical.
Caution ! If incorrectly adjusted, the filter can overflow and the
pond will be drained.
to remove excess nutrients while at the same time increasing the
oxygen supply.
The growth of algae can be restricted by installing a filter. Floating
substances (e.g. floating algae), which cause the water to be
murky, are filtered out and the water is purified. This helps the
pond to regain its biological balance. However, existing algae (e.g.
thread algae) visible at the time of installation must be skimmed off
(e.g. with the GARDENA combisystem Pond Sieve, Art. No. 7933).
Use of the UVC light reduces growth of algae. The algae solidify
and disease-causing bacteria are destroyed.
Installing a filter
Use of the UVC light
Functions of Your Pond Filter
3 /4”
1”
1 1/ 4 ”
1 1/ 2 ”
If necessary, assemble the
universal fitting and water
deflector after dismantling