How do I prevent thrush from happening to my breastfeeding baby?

When I was breastfeeding, I freaked when I saw that my son's tongue was white. I didn't breastfeed my 1st child, so this was a first for me. It doesn't seemed to bother my son much, but I got him NUK's mouth wipes and used it to clean his tongue and gums religiously after each feed. NUK's mouthwipes are expensive, but I love it because it's individually sealed so it doesn't dry up quick and its big enough to cover my finger even after I fold it once. You can buy it purchase it in bulk at the upcoming baby fair in April at the Singapore Expo. Alternatively, you can get it at Kiddy Palace. It's about $17 if I am not mistaken.