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How to Lower TDS in Aquarium

how to lower tds in aquarium

A high concentration of TDS or Total Dissolved Solids is not suitable for your aquarium and the fish because it can reduce water clarity while decreasing photosynthesis in aquatic plants. The high concentration can also combine with metals and other toxic compounds to increase the water temperature.

So, it is a must to constantly monitor the TDS level and keep it at the desired level. But how to lower TDS in Aquarium if it is too high? Check various tips and tricks we have listed below.

Do Water Change Regularly in the Fishtank

When learning how to lower TDS in freshwater aquarium, you must need to know that the TDS level is all the things you put in your aquarium. Whether it’s the food or the vitamins or anything that you add to the water will contribute to the higher concentration of the TDS. So, the TDS concentration will also go higher as time goes by.

If you keep the water in the tank for a long time, it is normal for the TDS levels to increase. But, to maintain or reduce it, then you must do water changes regularly. But how often will depend on how fast the TDS builds other water. So, checking the TDS level regularly is also very important.

Avoid Overfeeding the Fish

If you ask why TDS increase in aquarium, it is because anything that you put in the water can increase its TDS level. And that includes the food that you are giving to the fish. Also, if you have the habit of giving more food to the fish, then it is likely that it will contribute to the increase in TDS levels.

It does not matter if you are in several fish tanks or just a single aquarium. The most important thing to do is give just enough food for the fish. No more, no less. Those uneaten foods which will float or sink at the bottom of the aquarium can help in starting the buildup of TDS concentration.

Having a Reverse Osmosis Filtration System

lower the TDS level

Using the Reverse Osmosis Filtration System is the most effective way to lower the TDS concentration in your aquarium. If you have this filtration in your home, the water in your aquarium will be filtered out of all the TDS elements.

This process can eliminate almost all of the TDS or at least reduce the TDS concentration to a very low level. If the TDS level reaches up to 500 ppm, this method is the best one to reduce the level up to 50 ppm.

Once the aquarium water undergoes this filtration system, it will significantly reduce the TDS level of your aquarium water. In effect, the water quality will also be very high because water quality was being filtered in its purest form through the filtration system.

Using the Process of Deionization

If the RO filtration system eliminates almost all of the TDS substance in the water, then the Deionization process will eliminate what is left from the RO filtration system. This situation is the reason why it is so much better to combine the two processes.

Deionization is also being used to completely eliminate the remaining TDs level in the distilled water. Deionization is also being used to treat hard water while producing soft water. But in the aquarium, it works best if it supports the RO filtration system.

Helpful Tips:

  • Each fish can survive different TDS levels, which means whatever fish you have in the aquarium, you need to maintain the desired TDS level for them to survive. The key is to know the TDS level requirement of the fish in the aquarium and maintain it all the time
  • A TDS meter will be used to monitor the TDS level of your aquarium. This tool will give you an insight into what substances are there in the aquarium water. This tool can also be used to measure the TDS level of new water before it will be added to the aquarium
  • Testing the TDS level can also be used when trying to add a new hardscape or other materials to the fish tank. If you try to soak stones in a bucket of water, it will result in increasing the TDS level, which means that the rock is dissolving
  • Using inert rock will not affect the TDS concentration. On the other hand, using limestone should make your aquarium water to 400 ppm or more. But make sure to get a fish that can survive around this TDS level
  • Using fertilizers in your planted fish tank can naturally increase the TDS level. However, most of the fertilizers are not toxic to fish unless you will try to overdose the aquarium


Learning how to lower TDS in aquariums is excellent knowledge to have as an aquarium owner. As you put more substance in the aquarium, it is normal for the TDS level to increase over time. We have presented different ways to lower the TDS level, and all have been proven to provide effective results.

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