The mold was in the dirt you put them in. Depends on the type. If the potatoes show signs of rot get rid of them. Plain water usually does best for starting them inside, but for those who prefer a solid medium, use a gromix or potting soil. They need temps in the high 70's or low 80's for good sprout production. Lokk at a your sprouted potato and you should be able to determine which end was attached to the vine (up) and which end continued as the root (Down). Usually the top is more rounded while the deep end tapers off.
{{gwi:10174}}

why not try slips?

see our presentation which shows how we get tubers to sprout, but slips in water until they root then plant out or when soil warm enough just plant slips and keep them watered until they take.

len

Here is a link that might be useful: lens growing sweet potato's & pineapples page

I've cut the sweet potatoes in half and suspended in water to grow slips. Some of the sweet potatoes have developed some white gooey stuff in the water. My plan which may be crazy is to rinse the moldy ones and dip into rubbing alcohol before replacing in clean water. Anybody tried this? Or maybe iodine?

mine also developed some cotton-wool like fluff down the bottom end submerged in water... what on earth is this? mould? the first lot of water i put in was slightly tepid, i reckoned that they like warmth so i put some lukewarm water in for the s.potato... I wondered if this might have made it mushy?

having the same fluffy white stuff that looks like mold or fungus. any pros out there to answer?

I've never had to start sprouts/slips by placing SPs in water, it can become a stinky mess with nasty slime/mold rotting away at the potato. Periodically changing the water may help to hold down the growing mess. When I dig up mine in the fall I'll wash them off and store them inside on a multi-rack for future use. By about this time (Xmas) many will start sprouting slips without the need of water or anything else. By Spring they're loaded down with slips and I'll carefully carve off the slips and insert/plant them into old used cell packs with a mixture of seed starter and garden soil. Within 3 weeks they're ready to transplant outside. Plus I can still use the SPs that the slips were taken from. No mess, no fuss.