Quick Overview
TDS is an acronym for Total Dissolved Solid.
In other words, it's about measuring the amount of particles other than water (H2O). It is expressed in PPM (particles per million). These particles are of all types: minerals, bacteria, viruses, heavy metals, chlorine, other organic and inorganic particles.
Use your TDS Meter to test the hardness and quality of your aquarium water.
18 ppm = 1 ° dH