TDS stands for total disolved solids and is a measurement of mineral salts. It is used to measure the purity of RO water. This can be measured by hand held dip type digital meters or inline meters that can be connected directly to an RO unit. For more information on the units available please see the product pages on our website.

Please see the below link for more detailed information on TDS.

http://www.theaquariumsolution.com/tds-what-does-it-mean-and-why-should-...