As it's a few days since we had a toilet query here's another, While in Albufeira in January A chap told me that he puts copper sulphate into the cassette, then in Tarifa a lady said she buys the cheapest washing up liquid for her toilet, Neither of them explained the advantages other than their being much cheaper than the green sachets that I use at about £ 1.30 a pop ( not plop) what do you use?