The right way to monitor TDS reading for aquarium

A TDS meter is not only useful to measure the quality of your water after it has gone through the RO process. If you are using the RO system to produce clean water for your aquarium, then you can use the meter to monitor the performance of the various filter system in your aquarium set up. If you need help on buying the right meter, check out my tds meter reviews on which one is the best for the money.


3 TDS meter readings to monitor

To get a complete picture of your aquarium performance, you need to measure the following 3 things:

  • Tap water
  • RO water before DI
  • RO/DI

The purpose of measuring of the first 2 readings is to analyze the performance of your RO filters. By knowing what is the TDM of the tap water and how it improves after the filtering, it gives you a sense of whether the RO filters are working or whether there is a need to change them for better performance after prolong usage.  The last number measure the condition of the DI Resin filtration.


Relationship between RO and DI efficiency

While measuring the readings can give you a sense of the condition of the various filters in isolation, it is better to understand the relationship between the readings to get a fully picture.

To do this, we need to first calculate the efficiency of the RO filter, use the following equation:

  • (TW – RO)/TW

For example, if your tap water reading is 200, and your RO water reading is 2, then the efficiency of the filter can be calculated as follows:

  • (200-2)/200 = 99%

A new RO filter tend to give you an efficiency of 98% so anything above is good.

Now, the problem starts when the numbers drops 2% below 98%. When this happens, it will start to affect the efficiency of your DI. In particular the life of your DI resin will be cut in half for every 2% drop in RO efficiency. Hence, it is important to check when your RO/DI numbers are not performing on what is the real cause i.e. the RO filter or the DI resin. The RO filter efficiency ratio can help to separate the two.



To conclude, A TDS meter is a very useful and cheap device you can use to measure the efficiency of your RO systems, be it for water consumption or for aquarium. To get the full benefit of TDS reading, it is good to understand the ratios and how one part of a system can affect the others.


Why measure RO/DI


Leave a Reply