Question
I have replants some african violet and some mixed ivys into a larger pot. This has been done three times now. Each time after a few weeks the soil turns white on the top of it. I have cleaned it out, I have empited it and started overwith a new bag of potting soil and the same thing happens. Is that mold? I thought that maybe I was over watering it so I went to every other week and the same thing happens. Any suggestions.  

Answer
Kathy,
It is possible that there is a small amount of mold on top of your potting soil, but it sounds to me like mineral deposits and salts are collecting on top of the soil.  This is from your water.  It could possibly be that you are watering too often.  This is difficult to tell; you have to be the judge of that with your finger, or with a hydrometer, (a small instrument that indicates soil moisture).   Regular tap water is fine to use for African violets.  The small amount of chlorine and fluoride are negligible, so violets will be OK.  However, hard water, (that is, water with larger amounts of minerals) is not good for any houseplants for long periods of time.  You could use rain water, distilled water, or a cheap and easy way to get your water "softer" would be to add about 1 drop of dishwashing liquid per cup of water for PLANTS ONLY.  This is not for pets or people.  The dish detergent has surfactants and water softeners in it that help the water penetrate the soil.  It won't do much for the stronger minerals, though, but you should start seeing a difference in the white residue.  NOTE:  Dishwashing detergent liquid, NOT the gel used for dishwashers.