8
Cultivation of microalgae:
After starting, the culture is slightly green. The light should be switched on now. The optimum duration of the
illumination for microalgae is 16 hours. Illumination of up to 24 hours gives only a slight increase of the growth
rate.
Under these conditions, the green colour of the culture increases and after some days you can start to harvest.
Under ideal conditions, you can harvest 1 – 1.5 l of algae culture per day. They can be removed via the pinch
cock at the bottom. The missing water is then replaced by fresh prepared and filtered saltwater.
Note:
Only
use perfectly clean cans or buckets to prepare the saltwater. Zooplankton may destroy an algal culture
completely in a very short time. The most important factor for successful long term running the algal culture is
to keep it perfectly clean.
Fertilization:
A few drops of a commercially available complete plant fertilizer are added to the water in the reactor. Do not
fertilize too much so that the aquarium is not over-fertilized when feeding the phytoplankton. If the culture
becomes yellowish, it must be fertilized. In addition, a commercially available iron fertilizer for freshwater
aquaria can be added. The harvested microalgae can be used to feed the zooplankton culture (wheel animals
or Artemia), but they can also be put directly into the aquarium as food for many invertebrates (mussels, spiral
worms and others).
Cleaning:
After some weeks of permanent culture, algae wall growth may occur at the reactor. As soon as the culture is
shaded by this and the algal production decreases, the reactor has to be cleaned. Therefore, the culture is filled
into a clean vessel that can be closed. The plankton light reactor II is now cleaned with warm water with a
suitable cleaning brush. The clean reactor is refilled with the old algal culture and freshly prepared saltwater
(1:1).
Harmful organisms:
If harmful organisms have entered the reactor - e. g. filamentous algae or algae feeding zooplankton, the reactor
has to be completely emptied and cleaned. Afterwards, the reactor is filled with freshly prepared saltwater. In
this case, you have to use a new pure culture.
Enhancement of the algae production by fertilization with CO
2
:
The algal production can be increased for several times if the culture is supplied with CO
2
in sufficient quantity.
For the CO
2
supply, you need a standard CO
2
unit. The CO
2
is directed from the CO
2
bottle via pressure regulator
and bubble counter with check valve into the algal culture.
For optimum dosage of CO
2
, we recommend to use a night shut-off to avoid a pH drop during the night.
Therefore, a solenoid valve is switched between the pressure regulator and the bubble counter. The best solution
- in any case - is to use an automatic CO
2
control unit with a pH controller. This ensures that only that much
CO
2
is added to the culture that is used by the algae. In addition, the pH is always kept in the right range. The
pH probe can be placed in the top of the plankton light reactor II. For marine microalgae, the pH should be set
to pH 7.5.
3.2. Zooplankton production in the plankton light reactor II:
Cleanliness is the most important condition also for the production of zooplankton. For starting, the plankton
light reactor II is filled with freshly prepared saltwater. As food, microalgae from the plankton light reactor II
are added, the colour is slightly green.
If the plankton light reactor II is run with rotifers, the culture mixture can now be added (Brachionus plicatilis
for saltwater). If Artemia is to be bred, the reactor can be inoculated with permanent eggs.
Cultivation of Zooplankton – rotifers (Brachionus):
For producing rotifers, we strongly recommend to use the complete 2 stage food chain. Brachionus cultures that
are fed with living microalgae are much more healthy and viable than cultures fed with yeast of liquid foods. As
it is not good for a rotifer culture to stay without food for some days, the microalgal culture in the plankton light
reactor II should be set up first before the zooplankton culture is started.
