The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.
TDS - Total Dissolved Solids
If you have an RO/DI unit, how do you know when it's time to change the filters? You test it with a TDS meter. Ideally, the unit will produce 0 TDS and when it starts to rise, it's time for a filter change.