Total dissolved solids (TDS) refers to the quantity of dissolved solids (including minerals, salts or metals) in the aquarium water. In other words, it is all of the organic and inorganic matter that is dissolved in our aquarium water. It is a very useful tool for any shrimp keeper. Because it can be used as a way of deciding on the frequency of when it is time to do a water change.
The reason why we need to know and should care about TDS, because all these solids in our tanks can cause a lot of stress to shrimp. They can affect their growth, impact their breathing, make them more likely to be prone to disease. If your TDS is either too low or too high, your shrimp can have a hard time making their exoskeletons (the same with your snails). They need a certain amount of elements in the water to do that.
It is easy to guess, that TDS is associated with water hardness (PH). However, there is no direct correlation here, because water hardness depends on the magnesium and calcium salts in it. While TDS shows the total amount of salts (chemicals) dissolved in water (including those that do not affect hardness). That is why the important part is that a TDS meter does not mean anything without some other results. Let me explain it to you.
About TDS Problem in Shrimp Tanks
The main problem is that Total dissolved solids include almost everything: minerals, salts, nitrites, nitrates, ammonia, dechlorinator, water conditioners, fertilizers, shrimp (snail and fish) wastes, etc. Basically, all those things are going to come out in this number. Even the hot water heater can change the TDS number because of the different set of pipes. In some cases, we do not even have to put anything for that (evaporation will increase your TDS).
However, that number means absolutely nothing without other information. It is not telling us anything. For example, you can get your “perfect” TDS number for the shrimp by simply adding some dechlorinator to your tank. Technically, TDS is ok but in reality, it is not!
Do you remember in Harry Potter the most popular sweets in the wizarding world? They had every flavor imaginable. There was also no way of telling for sure what flavor any given. Almost the same is here with TDS. You have the number but do not know what is behind it.
Nonetheless, if we start using other test kits, it can start making a lot of sense. I will repeat that it is not possible to know let’s say how much hardness you get until you test it for GH with test kits.
The TDS indicator itself is not informative, and it makes sense to measure it only if the salt composition of the water is known. That is why, when we are speaking about TDS, it is necessary to know which particular salts determine this value.
On the other hand, we can see a clear correlation between the TDS and the hardness (GH) when we remineralize RO water with a certain kind of salt. Of course, this correlation will be true only for this particular type of salt. This is very convenient when we are preparing water for water changes in our tanks. Once you know the dosage of mineralizing salt, stick to it in the future and simply repeat the same process.
Note: Ideally, to measure TDS you need a TDS-meter, calibrated for a specific type of salt. This is due to the fact that the TDS-meter measures the conductivity of water (and it is different for each solution). Typically, they are calibrated with a solution of sodium chloride. Strictly speaking, if you decide to measure TDS of other salts, the readings can be different. However, in most cases, the difference is not significant and it can be neglected.
Examples of TDS and Types of Shrimp
|150 – 200
|100 – 300
|Caridina cf. babaulti
|100 – 150
|50 – 250
|150 – 200
|80 – 300
|Crystal red shrimp
|140 – 160
|100 – 250
|150 – 200
|100 – 400
|150 – 200
|100 – 400
|150 – 200
|100 – 400
|50 – 150
|Blue tiger shrimp
|180 – 220
|100 – 300
TDS vs pH, KH, GH
Sometimes people become too enthusiastic and start prioritizing TDS over other water parameters in their tanks.
Well, this is a good way to find a lot of problems for your shrimp. There are many examples when shrimp can live and thrive in suboptimal TDS (not critical of course). Well, it can sound contradictory but although TDS numbers are important they are not written in stone. Keep in mind the golden rule – Do not fix it if it is working for you.
Remember that TDS number does not tell what things are dissolved in that water. It is a very useful test only if you combine it with other tests.
TDS and TSS in Shrimp Tank
Total suspended solids include all particles suspended in water which will not pass through a filter. Basically, these are particles that are larger than 2 microns. Anything smaller than 2 microns (average filter size) is considered a dissolved solid (TDS). They can flow through the filter media (too small to be trapped).
High level of TSS can be also dangerous to the shrimp. In some studies, biologist reported that higher suspended solids concentrations may have clogged the gills and committed to respiration of the shrimp.
Why TDS is Rising in Shrimp Tank
Actually, it is a normal process and you cannot do absolutely anything to stop it from rising naturally.
The TDS increases because we are always adding things into our shrimp tanks. Almost everything that we add into out tanks can impact the TDS. This includes your fertilizers, water conditioners, minerals, foods etc.
Sometimes we do not even have to do anything for that. Due to water evaporation in your shrimp tank the concentration of salts increases (they do not evaporate with water). Therefore, take it into account as well when you remineralize your water.
How to test your tank for TDS
In order to test for TDS, you need a TDS meter (link to check the price on Amazon). TDS-meters are super easy to use. Dip the TDS meter into your aquarium or any other water and it will give you the result. The numbers will be shown in parts-per-million (PPM).
What it does is it measures the electrical conductivity of the sample water. The thing is that water does not conduct electricity, it is the dissolved chemicals in water that conduct the electricity through it. Water in and of itself does not conduct electricity. Therefore, the more electrically conductive a sample of water happens to be the more chemicals that there are dissolved in that sample.
Tip: If you are buying a TDS meter for the first time, make sure that it measures in parts-per-million (PPM). Otherwise, you will have to convert parts per trillion or all parts per thousand into PPM. It is very inconvenient.
How to Calibrate TDS-meter
- Measure exactly one liter of distilled or RO water (in which, ideally, TDS = 0).
- Dissolve exactly 500 mg of the desired salt in it.
- Adjust the readings of the device (there is a special screw), to the number “500” on the display.
Note: It is recommended to calibrate the TDS-meter once every six months.
Tip: Prepared calibration solutions are sold in the pet stores and are very inexpensive. TDS-meters are usually calibrated using a solution of Sodium chloride NaCl.
How to lower TDS in Shrimp Tank
If you find yourself in a situation where you have got TDS levels that are much higher than you would like and you want to bring them down the way to do that is by dilution. Basically, by adding RO or distilled water. That is a common saying the solution to chemical pollution is dilutions.
The reason is that adding more chemicals is not going to work. In terms of TDS, you cannot add chemicals to get rid of other chemicals. Adding chemicals will only increase TDS numbers.
- Prepare RO or distilled water.
- Add some minerals in the water (much lower than in the tank).
- Do your water change.
Note: Some shrimp breeders do not even add minerals if they need to lower TDS number more significantly. Personally, I prefer to play safe and add at least some minerals. However, if you do not do big water changes, slight changes (5-10% max) with just RO water it should not affect your shrimp and should not cause any molting problems.
TDS meters are great when you know what the number actually means that it displays. It is better to use them in addition to other test kits (GH, KH, and pH) we have available to us in the hobby. GH, KH, and pH form Bermuda’s Triangle of water chemistry. Although the three properties are distinct, they all interact with each other to varying degrees (and effect TDS), making it difficult to adjust one without impacting the other.
In all other cases, there is no reason to put blind faith into TDS readings as an indication on whether your water is right for the shrimp or not.