[engineer]

I have an IBC container which is clear and in direct sunlight, the water contents soon turn green and appear to be fermenting, i have covered it in black polythene to keep the sun off
 it , but was wondering is there anything i can add to the water to prevent it going foul 

[angelavdavis]

It is probably blanket weed developing in it - it does look like it is fermenting when it is bubbling up the top.  If it is possible, you could put a long cane into it and twirl it to remove the worst.  Usually people add barley pellets or extract of barley straw (both can be bought from suppliers like www.harrodhorticultural.com) into ponds that develop the same problem.

[GrannieAnnie]

From suggestions on here, I've put charcoal in my green water butts, that seems to be keeping the water clear, and I got some stuff from B&Q for my IBC tank that is supposed to keep the water clear, but I don't know if it works yet as OH wants to move the IBC, but can't decide where its going!

He'll probably wait until the rain stops for the summer, THEN he'll move it!   

[mumofstig]

You can add Citrox to the water to keep it sweet

[engineer]

Thanks all for the suggestions, Mum i had heard of Citrox but couldn't remember the name, cheers