Im wondering if anyone else experienced this. I have a 30 gal grey brute food safe can I use to mix my salt water. Nothing besides RO/DI water, salt mix, and a submerisble pump goes into this container. I just happened to open my container during the day. Salt water had been mixing in this since a day prior. In the daylight I noticed that the bottom had a brown filmy substance. I thought at first it might be something coming off the pump so I took it apart but found nothing like that on the inside. Any ideas?