Just purchased a HM digital com-100 TDS meter and have a few questions about something I found. My current set for making water is as follows. I make ro-di water that fills a 30 gallon brute. I normally make water on the weekends and leave it until i need it for top off or make a bunch in anticipation for the bi-weekly water changes. I tested the water right out of the ro-di unit and i am getting 0 on the TDS meter. I tested it again after it sits in the ro-di brute for a bit and it reads 1.4 at that time. Now here is where I have some questions on why and what to do. When i get ready to make salt water I manually transfer 15 gallons (by a 5 gallon bucket) into a separate 30 gallon brute. In this brute is a heater and a power head. I just tested the water in the saltwater brute (no salt added, just barely transfered from the ro-di water brute) and it reads 64.5! The only thing this brute has been used for is to mix up salt water. Why is this reading so high? Is it the old salt that dried on the bottom and sides of the brute from the previous saltwater mix? Should I clean this brute? If so, how? Is this number normal? How do you keep your saltwater mixing containers clean/clear? Thanks!