hello I'm new to saltwater and to this forum so please be gentle. i have an ro/di system and it has been up and running for about two months, the other day i went down to add salt to the one tank and noticed what looks like black algae or some kind of mold on the sides of the container under the water line. i used two grey 35 gallon trash cans for storage and the fresh water tank is crystal clear, i keep lids on them at all times and the water is heated and circulated also. does anyone have any idea what this might be or how to fix it. obviously I'm emptying the container and cleaning it then going to refill it to see if it happens again but any helpful advice would be appreciated.
