water butt - slight problem also in SY

[louisevictoria]

When we moved to our new place all of the stable block was already sorted, with a water butt at the end, collecting the rainwater from the roof.
Unfortunately it is one of the big square, transparent ones and in direct sunlight so the water is now starting to go slightly green

Is there anything I can do to stop this or is it a case of, every couple of weeks empty it completely and give it a good blast with the pressure washer?

Help please

[Enfys]

I have no idea whether this would work, but perhaps if you painted it?

[BigRed]

I only use the water from my roof for the garden, so I don't care whether it goes a bit green.

[Box_Of_Frogs]

You could put up a bamboo screen (see last 4,000 episodes of GroundForce lol) that would shade it, but TBH you still have the ambient temperatures to contend with. A more workable solution is to persuade your OH (or any suitable male) to get on a ladder and re-direct the roof run off somewhere not in full sun. Even if you did that, unless the water is constantly changed you will get algae in it. The only other alternative is to get a filter pump with UV light that destroys the algae as the water is pumped past. Costs? Option (a) approx zero or maybe few bottle beer to give OH/other male. Option (b) between £500 and £1,000 but you would have sparkling water all year round!