gdogfunkanswered grow question 5 years ago Hello! I am a huge fan of URB and came across your diary. I believe the white spots you are seeing on the fabric pots are nothing more than leeched salts from the nutrients and not mold. I get them on my fabric pots as well. Over time, the buildup can cause the fabric to get clogged and the aeration is not as good due to the restricted air flow. I usually replace the pots after several uses since the buildup can get extensive. You can spend the time to soak or wash the pots, but in my experience, it is just easier to buy new fabric pots when the residue becomes a problem. I would also recommend putting something under the fabric pots to help allow the bottom to drain better. I hope this helps! Let me know if you have any other questions!