Use diluted bleach and a firm scrubbing brush. Turn on the fan and open windows if you have any. When you are done rinse with plenty of water. Once you've got the mold off then you can clean the tub with baking soda and vinegar but you have to do it regularly or else the mold will build up again!
I use BS and vinegar. Its also good the clean goo from the drain and pipes.<br><br>
Since it foams up you tend to feel like you cleaning with a commercial cleaning product. After your done cleaning pour some boiling water over the tub and down the drain. I just use a tee kettle full and that seems to do it.