Planted Tank Obsessed
Join Date: Apr 2015
Location: Westchester County, NY USA
TDS meter gives an ability to get an idea about how much stuff is dissolved in the water in a fast and easy manner, so it is very useful if you are playing with water parameters (mixing tap with RO etc.) targeting specific water hardness for sensitive fish and shrimp. Makes it really easy to detect if substrate leaks something into water. Basically, it is much easier to measure TDS than to do GH measurement.
If you don't play with water hardness and don't have sensitive shrimp (e.g. CRS), you don't need it, otherwise it is invaluable.