kombucha

To prevent Mould on your culture:

Make sure there is no mould spores on the tea leaves that you are brewing.
The brew must reach a certain PH, not having enough mother liquid could mean that the brew is not acid enough and mould spores could grow.
Your brew may be close to a compost or rubbish bin where mold spores may contaminate the mother culture.
Cigarette smoke can cause mould to grow on a culture.
The cloth you use to cover the fermentation container may have to wide holes allowing mould spores to penetrate through to the scoby. Use a tightly woven clean cloth secured over the mouth of the brewing vessel. Doubling it over may help in preventing mould spores from getting on the culture.
Gently rocking the brewing vessel once a day is a very effective way of preventing mold from growing on the culture. Make sure not to rock it to hard or the developing culture will sink to the bottom (don't worry it will form another on the top of the brew again)- Image Below
Instead of rocking the brewing vessel, fill a jar with some mother brew and every day, use a plastic teaspoon to gently pour some of the mother liquid over the culture. All that is needed is enough to moisten the culture. Image below
Living in the tropics where constantly high humidity levels exist for the majority of the year can make it difficult in preventing mould.

Room temperature can effect the speed of growth. If the culture is struggling to grow mould may develop. The best growth is in the range of about 80° to 85° Fahrenheit. However, 21°Centigrade = 70° to 75° Fahrenheit is usually sufficient to grow the Kombucha mushroom.