On Mon, 23 May 2011 13:28:25 +0100, Jake wrote:

Maybe something like this:
http://www.gardencentre.co.uk/produc...r=gbase&ad=860

Ah, something to stop the water going stagnant or growing Alage.
Algae needs light to grow so a decent opaque lid and side cures that
one. Stagnant would require quite high volumes of organic matter I
would have thought, not just atmospheric fallout or tile/slate
debris.

Like David I don't "treat" ours. The last time I emptied it 'casue
the silly plastic tap broke there was about half an inch of very fine
black mush in the bottom and a healthy population of blood worms...
Not much organic or other matter makes it into the butt though as the
hosepipe feed has a deep dip in it that traps most grunge and needs
emptying every year or so.

--
Cheers
Dave.