I've been using my perfect prep machine for almost 6 months and just went through the second filter change. I took out the water tank and filter and underneath (where the water goes after it's been through the filter) was full of black mould!!!!! Am I not looking after it correctly??? My husband did the last filter change and said he followed the instructions and there was no mould or anything. I took the tank out, washed it, got rid of the air bubbles in new filter, put it through the cleaning cycle, and of course washed the inside of the machine thoroughly. My poor daughter had sickness and diarrhea last week and I'm wondering wether this is the cause?? I feel so bad at giving her dirty water for her bottles. I re-read the instructions and im sure I'm doing it right. Since last week I've been making more fresh bottles because now I'm scared to use it!