In transparent one layer tanks, algae grow due to the passage of light through the tank wall. (You can place this type of tank in a dark place to prevent them from algae).
These types of tanks are not suitable for long-term water storage.
Note that polyethylene by itself does not cause the growth of any algae, and only transparent tanks will absorb algae due to the passage of light if the water stays in them for a long time.
So the color and layers of the tank (if there is a black layer) have no effect on the growth of algae in the tank.
Yes, a safety ventilator must be installed in any case.
Reliable ventilation to eliminate positive pressure when water enters the tank, which if the floater or water pump does not stop, the water comes out and prevents the pressure of water entering the tank and negative pressure (when the water leaves the tank replaces the air ) Is used.
Horizontal tanks due to having bases and parts that use more materials to form. They weigh more andtherefore have a higher price than verticaltanks,
although this is not a reason for higher quality or longer life.
Usually, when the water stays still for a long time, the quality decreases due to lack of oxygen and may change in taste, but due to the fact that in the Shadman polyethylene tanks there are no materials that can be combined with water so there are no changes in the stored water and the change in the taste of water in a long time is only due to the reduction of oxygen and stillness of water that occurs in any other container.