If much of the algae is in the tubes, I would fill them with a much higher concentration of bleach and water in the tubes and let them sit over night. Run some water out to flush the bleach out in the morning. This is called a"shock" treatment.

Chlorine bleach is similar to what is used in swimming pools. Most RV water systems recommend putting a teaspoon of bleach in the water tank when filling. It is not harmful at low concentrations but if your problem is tough then use a shock treatment and flush it out before using it. May be a good idea to scrub the cattle watering tanks out with a brush and high concentration of bleach also. Then flush/rinse them out and refill with clean water with just a couple teaspoons of bleach depending on the size of the tank.

Sorry but I have no idea what the metric equivalent of a teaspoon is!

Good luck!

Jim at Dawn