Conserving and maintaining the crop
In order to increase the quantity of the Spirulina it is possible (but not necessary) to move the crop from bottles to pools.
Any basin can be used for a pool – a bowl, a tub, a water resistant sheet of plastic.
If the walls of the basin are transparent (as the bottles are) – a basin of any depth can be used because sun light will reach all the algae.
If the walls are not transparent – the optimal depth is 30 cm.
The algae can be stirred using a stick or a broom. If a small pump (the kind used for fish aquariums) is available – it can substitute the manual stirring.
A cover for the basin is needed to protect the algae from direct sun light as well as from rain which will dilute the culture medium.
When liquid level has lowered (because of natural evaporation that may vary in different climates) – water is added to the growing culture and ph level is tested.