So after several weeks of declining conditions in my tank (algae growth and general unhappiness of corals) I tested the ro/di water in my holding containers that I use for top offs and water changes. The TDS was 500! First thought was somehow the waste line got use to fill instead of the fill line. However, the waste line never leaves the drain and is labeled. I have a tds meter on both incoming and out going lines. It usually reads around 300 incoming and 000 outgoing. Also, nitrate and phosphate levels in the tank are at zero. I would expect that there would at least be measurable amounts if the waste line was being used. My containers are 5 gallon nalgene. Has anyone ever heard about nalgene leaching stuff back into the water? Ideas?