Harvest your spirulina
When should it be harvested?
Harvest spirulina when the spirumeter disc (also called Secchi) is no longer visible at a depth of less than 5 cm.
The Secchi is used to determine the concentration of the spirulina. Immerse the white disc in the tank; the concentration corresponds to the depth at which the disc disappears
Quand récolter sa spiruline ?
A few tips…Harvest early in the day: spirulina has its best nutritional qualities early in the morning.
You can switch off the aeration system one hour before harvesting: the spirulina will rise to the surface of the tanks and will therefore be easier to harvest.
Installing the equipment
Components included in the harvest module
Cleaning the equipment
Disinfect all harvesting equipment with white vinegar, then rinse with water:
- Filtration containers;
- Spirulina filter;
- Beaker and Secchi disc;
- Harvesting spatula.
Setting up the harvesting device
Using the skimmer net 🅐, remove any biofilm present on the surface, clean the edges of the tank using the cleaning brush 🅐, then remove the residues again with the skimmer net. Move the aeration system (air pump / aerator) to another edge of the tank so that you can place the filtration device.
Place the filtration tray 🅐 at the left end of the tank, with the nozzle facing outward.
The filtration device consists of an upper part used for filtration (grid 🅐 ) and a lower part (metal tray 🅐). Place the spirulina filter 🅐 on the filtration grid 🅐 by folding the edges of the filter over the back of the grid, then place the covered grid on the tray 🅐.
Attach the filtration hose 🅐 to the pump (position "deflate") 🅐 and connect the other end to the nozzle on the side of the tray. Plug in the pump without switching it on.
Vacuum filtration and harvesting fresh spirulina
Collecting the liquid spirulina
Switch off the tank aeration system.
Fill the 1 L beaker with spirulina concentrated at the surface.
Filtering the spirulina
Pour the contents of the beaker🅛 onto the harvesting device. Check that the filtrate flowing through the hole under the tray 🅘 is clear. Wait for the excess water to drain away, then repeat the operation until the filter is saturated (slow passage of the medium through the filter)🅗.
Starting the vacuum pump to speed up filtration
Switch on the vacuum pump 🅚. When the medium has been almost completely filtered, switch off the pump.
If the filtration flow rate does not seem to increase:
- check that the upper part of the container is fully inserted into the lower part
- check that the filter is pressed firmly against the grid thanks to the folded-over excess
- check that water is not flowing into the air hose towards the pump
When the medium has been almost completely filtered, switch off the pump and open the valve to prevent the lower container from overflowing into the pump.
Stop a little before the medium is completely filtered: this helps avoid pressing the spirulina and therefore saturating the filter too quickly.
Rinsing the spirulina
Once the medium has been filtered, rinse the spirulina with 1L of water, then switch on the pump 🅚 again until the medium is completely filtered.
Harvesting the spirulina
Using the spatula 🅑, collect the pressed spirulina in a food-grade container.
If the quantity of spirulina harvested at this stage is too small, repeat the filling and filtration steps as many times as necessary (harvest every 5 L to increase filtration speed by limiting filter saturation).
Regularly check that the tank Secchi reading does not drop too much: ideally, it should be between 5 and 6 at the end of the harvest.
Weigh the harvested spirulina so that you can calculate the quantity of culture medium that will need to be added afterwards.
Cleaning the harvesting equipment
At the end of the harvest, rinse all the equipment used with water.
Rinsing the equipment quickly after harvest helps prevent the spirulina from drying and becoming more difficult to clean.
Once dry, store the equipment in a clean place, for example in the module's technical box.
Do not forget to reconnect the aeration system and return it to its initial position.
Weigh the mass of fresh spirulina harvested so that you can calculate the quantity of culture medium that will need to be added afterwards.
If the filter seems to saturate very quickly, you can soak it for 24h in vinegar to remove any material that may have accumulated on it.
Tank nutrition after harvest
Depending on the mass of spirulina harvested, the culture must be replenished with salts: add 1 g of the nutrient salt mixture per gram of fresh spirulina harvested.
Remember to check the pH of the culture using pH paper. It must be between 9 and 11.