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.
ImportantThe 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
| Name | Optimal TDS | Limits |
| Bamboo shrimp | 150 – 200 | 100 – 300 |
| Caridina cf. babaulti | 100 – 150 | 50 – 250 |
| Snowball shrimp | 150 – 200 | 80 – 300 |
| Crystal red shrimp | 140 – 160 | 100 – 250 |
| Ghost shrimp | 150 – 200 | 100 – 400 |
| Amano shrimp | 150 – 200 | 100 – 400 |
| Cherry shrimp | 150 – 200 | 100 – 400 |
| Cardinal shrimp | 100 | 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
From time to time you can also see the term Total Suspended Solids (TSS).
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
You can calibrate the TDS-meter for salts (minerals) you use by yourself. In order to do this, you need to:
- 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.
Conclusion
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.
TDS Meter and chart is only for Shrimp? TDS number chart for freshwater water fish unable to find this should be for able for all fish
I am pretty much sure that it will suit your fish. The point is that many aquarists have community tanks (fish, shrimp, snails). The chart shows only the optimal numbers.
Hi there. Very good article! But a have a doubt. In the table “Examples of TDS and Types of Shrimp” the TDS values are expressed in PPM or µS/cm? Thank you.
Hi José Victor Martins,
It is PPM.
Best regards,
Michael
Thank you for replying. I think 1 PPM = 2 µS/cm, isn’t it? So the optimal TDS range to crystal red shrimp is something among 280 to 320 µS/cm, could you confirm? Thank you.
Yes, in general, it will be so. According to different calculations, the margin for error of measurement is 2%.So it can be neglected.
Best regards,
Michael
good topics for fish farming.
Hi Michael!
Great website! I just started my shrimp tank, which is a very small tank at 10 US Gallons (it’s a Fluval Edge).
Should I bother with getting an RO/DI unit? If yes, can you recommend one?
Thanks,
Audie
Hi Audie,
Thank you for the kind words 🙂
Regarding your question, it depends on the shrimp species you are planning to keep. For example, Neocaridinas can live in tap water.
However, if you want to create an optimal condition, in this case, I will definitely recommend getting an RO/DI unit.
I even wrote an article about it “7 Things Every Shrimp Keeper Must Have!“.
Personally, I still use the cheapest Aquatic Life RO Buddie. Well, maybe there is something else/better on the market, I can’t say.
Best regards,
Michael
Hi Micheal.
Your article has been very helpful, thank you.
I have RCS in an 350lr aquascaped aquarium. I’ve just received my TDS meter and tested my tank water, which reads 478ppm that I feel is way too high. I do have access to rainwater with parameters: pH 6, GH <15, KH 0 & TDS 18. However, I tend to use dechlorinated tap water, which is pH 7, GH 120, KH 80 & TDS 348.
On paper, the tap water seems to have better overall parameters. However, should I maybe use a mixture of the two during water change, to help bring my TDS down over time?
Thanks for sharing all your knowledge!
Christine
Hi Christine Hearne,
First of all, how do your shrimp feel? Do they breed? Do you have losses? Are there molting problems?
The reason I am asking these questions is that I would not change water parameters if your shrimp are OK and breeding. Where did you buy them? Do you know water parameters they were kept in before? This is very important.
Yea, even though these water parameters are not optimal as we (aquarists) think, those shrimp could have adapted to them. Therefore, any changes will only harm them.
Do not fix it if it is not broken.
However, if you do need to fix your water parameters, in this case, I would not mix tap water and rainwater. We usually have no idea regarding our tap water chemistry. So, use it only when you do not have any other options.
Best regards,
Michael
Hi, I have been keeping RCS for years with very limited success, the odd shrimplet but could not keep the colony going and had to purchase more shrimps every few years. After years I have found you must be able to grow java moss successfully in your tank. The shrimp feel safe with lots of moss and now I have loads of babies. Lights on twice a day 4 hrs each. Water tds
380- 440 PPM.
Hi John,
Thanks for sharing your experience!
Best regards,
Michael
Hi Michael
Many thanks for your reply.
The person from whom I bought the shrimp said they used tap water, which was why I thought I should continue. I’ve only had the shrimp 4 weeks, in a mature tank with fish. To this point, I have not seen any fatalities. Three of the adult females are now carrying eggs and none of the shrimp seem to have any molting problems.
As you suggest, I wont try to fix what ain’t broke!
Great advice, thank you.
Hi, Michael. Do you think a TDS of 200 us/cm (microsiemens, not PPM) is too low for crystal red shrimp? Or this level is good enough? Thank you.
Hi Victor,
Even though it is a little bit on the lower side I would not recommend you to chase the numbers!
1. Ideally, you need to find out the water parameters they were bred in. Ask the seller. By changing them to recommend, you can stress them.
2. However, if you do not know the water parameters your shrimp were bred in, in this case, it will be better to follow some recommended numbers.
Best regards,
Michael
Michael,
Hi. Great article thanks (actually all your articles are great).
I do add aquarium salt to my freshwater aquariums (I have a 55 gal tank and a 10 gal tank) – both have different varieties of Shrimp a well as snails and other tropical fish. I normally add one tablespoon of aquarium salt to 5 gals. I also only use RO water (recently started – mostly on the 10 gal tank).
Would adding aquarium salt dramatically impact the GH/KH/TDS readings? Currently my readings are as follows:
10gal GH=5; KH=7; TDS=562
55gal GH=20; KH=6; TDS=2590
The 55gal is very high in GH/TDS and I’m in the process of replacing 10%/day with RO water..
Any comments? Should I stop using aquarium salt?
DaveJ
Hi David Jackson,
Thanks!
Why are you adding aquarium salt to your freshwater tank? Are you treating your fish?
Although it is true that it can provide fish with essential electrolytes … it is also a problem because different species require different dosages… So, it can be really hard to balance in a community tank.
Aquarium salt is basically pure, untreated sodium chloride (NaCl), and sodium chloride does not affect either KH or GH. However, it increases TDS. I think that is why your TDS is so high.
Best regards,
Michael
Thanks Michael,
That does make sense, and was my first suspect for such high TDS in the 55 gal tank. The only reason I’ve been adding aquarium salt to a freshwater aquarium was for the “medicinal benefits” so claimed by many freshwater aquarium enthusiasts..
I’m not too worried about the 10 gal tank – it seems stable and will not add any aquarium salt from now on. For the 55 gal tank the same, but will do a 5-10% water change every day using RO water until the TDS attains a more acceptable TDS/GH level. I’m not too sure how long that will take ?? Any other suggestions would be truly helpful.
Thanks again !!
DaveJ
Hello Michael,
The current TDS of my tap measures at 156, and the place I plan to ordering shrimp from has TDS at 250-350. Do you think drip acclimation would be enough to bypass this difference, or would it be a good idea to just add some minerals to my water beforehand and re-test the TDS after that?
Many thanks,
Eric
Hi Eric,
Well, yes and no.
TDS (as a parameter for shrimp tanks) is a little bit tricky.
Your tap water TDS and TDS of reminerilized water have two completely different meanings. Even if they are mathematically equal.
You don’t know what kind of minerals are in your tap water!
Therefore, it would be wrong to talk about balancing your tap water TDS and TDS from other water sources.
Personally, I don’t support the idea of using reminerilizers and tap water.
As I have already mentioned, you have no idea what minerals are already in tap water, and by adding mineralizers you get some uncontrollable quality of water. As a result, your TDS does not show you the correct numbers.
What I mean is that if you take RO water and add baking soda you will increase your TDS – but these ‘minerals’ are useless for us.
Best regards,
Michael
Thanks Michael,
That’s right, I tend to forget about the simple fact that TDS measures the quantity rather than the quality of the dissolved solids in water; that’s a very important concept that I needed reminding on, despite it being in the first line of this article. 😂
Best,
Eric
Great article! I have an established 20 gal tank of 3 years that I converted into a shrimp only tank for my neocaridina shrimp about 2 months ago. I also have one bristlenose pleco and a mystery snail.
In the past two months, I have added live plants such as hornwort, Christmas moss, Java fern and Anubia. I have inert substrate.
My water parameters are currently as follows:
72 degrees
GH 8
Nitrite 0
Nitrate 25
Chlorine 0.8-1.5 (without prime)
KH 4
pH 7
TDS 415
I have very hard tap water, so I use an RO unit that I remineralize with Shrimp mineral GH/KH+. I’ve been slowly trying to remove 5% water 2x/week and replenishing with new water.
About a month ago, I started noticing KH and pH drops. I added a small bag of crushed coral to my HOB filter. I also should add that I added a sponge filter for extra filtration and oxygen. I started to notice that I would get chlorine readings on my test strips almost every morning or every other morning. I would dose the tank with prime and it would register as 0. I don’t understand the chemistry enough as to why chlorine would show up in my tank as I do not add any untreated water. Could it be the crushed coral? Is it old tank syndrome combined with crushed coral? Could it be the shrimp mineral? I have removed the bag of crushed coral in the meantime.
I have lost several shrimp in the past two months, but currently the shrimp have been doing well – several berried and I see shrimplets, and my mystery snail had laid many clutches, but the chlorine readings worry me and I end up dosing prime directly into the tank whenever I notice it. But, if I’m not in town for a period of time over a few days, I’m worried that the chlorine levels will rise and I will come back to the entire colony being wiped out.
thanks in advance for any insight
Hi Jennifer,
Frankly saying, I do not think that your problem is because of crushed corals. After all, they are comprised of Calcium Carbonate.
Even more, according to some studies, Calcium Carbonate can even adsorb and thus remove chlorite and chlorate from the water.
When did you change your reverse osmosis filters the last time?
So far, it is the most probable version.
Best regards,
Michael
I appreciate your quick reply! Just changed the RO filters about 3 weeks ago. More recently I have been buying gallon jugs of distilled water and mixing the remineralizer. It’s baffling to see some chlorine readings a day or so afterwards!
Thank you for easing my concern about crushed coral. I am still at a loss…
Hi Jennifer,
It’s really weird.
Let me clarify some things.
When was the first time you noticed chlorine? Was it before or after you changed your filter?
Have you tested your water before adding it to the tank? Is it possible that this new filter doesn’t work properly?
As I understand, you removed crushed corals. Did you see any difference? Although, they should not be a problem … but in your situation, you need to exclude any options.
Best regards,
Michael
What could happen to shrimp if TDS is too high?
Hi Steven,
In the best case scenario, they will stop breeding.
Best regards,
Michael
Dear Michael, Your posts are always insightful and valuable. Thank you!
Hi Robbin,
Thank you for the kind words! I do my best 🙂
Best regards,
Michael