If you want to disinfect it properly and kill any nasties lurking, you'll need to use something stronger than washing up liquid. When cleaning my viv once a month, I mix water and bleach in a ratio of 10:1 to dilute it to 10%, then scrub it out. Rinsing properly afterward is very important. Get a sponge, soak up and get rid of as much of the bleach water as possible, and pour in a load of fresh water and rinse it around thoroughly. Soak up and wring out that water, then rinse it again with fresh water, soak it all up then let it dry. That'll do the job. If you're not sure if you've rinsed enough, take a look at the water you're wringing out and ask yourself whether you'd want to drink it. If you can still see bubbles, you haven't!
