Questions about TDS meters - The Planted Tank Forum
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post #1 of 9 (permalink) Old 11-25-2019, 09:18 AM Thread Starter
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Questions about TDS meters

I have read in several posts references to TDS values in aquariums and the use of TDS meters. Since Iím not really familiar with them Iím wondering how these meters work and what exactly are they measuring? Is a TDS meter something that every fish keeper should have in their equipment arsenal or is it just one of those ďnice to have but not essentialĒ items? How important is it to know the TDS level in oneís tank? Advance thanks to any kind soul who can shed some light on the subject!
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post #2 of 9 (permalink) Old 11-25-2019, 05:24 PM
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TDS meters actually measure the electrical conductivity of the water, and convert to Total Dissolved Solids based on some standard solution. Not sure if it is based on a straight NaCl solution, or a mixture of chemicals.

I use it to monitor my aquarium water, as my tap water has high TDS (~400-450 ppm). During periods of high evaporation, my tanks can exceed 500 ppm if I'm not diligent with water changes. My Crypts, especially, don't like TDS above 500.
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post #3 of 9 (permalink) Old 11-25-2019, 11:15 PM
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If your fish and plants are doing good and you do regular , as in weekly , water changes , and you aren't keeping any special fish that are TDS sensitive , I wouldn't worry about TDS . Meters are fairly inexpensive if you want to get one and check for curiosity's sake . Up to you and your situation .

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post #4 of 9 (permalink) Old 11-25-2019, 11:18 PM
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@Edward does a good job of explaining it here: https://sites.google.com/site/aquati...home/tds-meter

Yes: IMO, it is something that you should use and they are cheap. Depending upon how much you want to get into the TDS readings, you can choose to get one that measures TDS on a part-for-part basis or buy one that is more typically sold in the US and, if you are interested enough, do a conversion.

Basically, though, all you need to do is use it as a relative measurement against other readings that you've taken and develop a general idea of what your readings mean. For example, I believe that fish should not be subjected to more than a 10% change in TDS in a day. Osmotic shock can kill fish and we now believe that it is osmotic shock and not pH shock (old wives) that is the killer resulting from uncomfortable water changes. I use it especially when acclimating new fish, as I want the the QT water to equal the TDS of the LFS water before dumping the new fish into it.

Plants can also be damaged by osmotic shock, but your fish are more likely to tell you that it is too much before your plants do.
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post #5 of 9 (permalink) Old 12-05-2019, 08:08 AM
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I have been in the hobby for a long time, but stopped for a variety of reasons. These things were not all that cheap when I left, but now $20 seemingly gets you a highly recommended one. I have my first and it has only been like 2 weeks, so take it with a grain of salt. First, my TDS were WAY higher in the tank than out the tap. I am experimenting with ferts and it being higher didn't surprise me, how high it was did. I did one EI dose after each water change and got an idea of how much it raised my TDS. Since EI should be excess (but isn't solving what seems to be a calcium deficiency by other peoples opinions), I could gauge a baseline of what I would ideally want. I have an amount of Equalibrium I know works, but it raises my TDS significantly. I am spreading that out over longer period of time, rather than one large dose after a weekly water change. My fish are more active, more colorful, and just healthier by changing that. Similarly, if one or more look a bit "off", my TDS is often higher than expected. Though I can't know exactly what is in my water, I have a better understanding. My fish are new, I would typically blame the LFS for a death or myself, now I feel I have some sort of data to know. I thought one of my Otto's died, it was just struggling. 2 partial water changes and it looks fine now. Then I adjust to make sure I don't over do things, especially since they are sensitive.

Next, I found I can have a TDS as low as 20 or as high as 90 out the tap. I don't know why, I do know that many water lines in my area are being routed differently as I live in a rapidly growing city, but I see my water source isn't consistent. I live in a very large condo complex so I don't know what type of filtration exists, if any, but have verified this happens. I know it isn't a calibration issue as I have put water in a glass and it doesn't change nor does my tank water when the tap does. Not necessarily important but good to know. If I see a larger swing, I may switch to RO, now that I have a shop in my area, I can't install an RO system very easily here given my limited space.

The biggest for me is changing water at a TDS level I feel safe with. This has been a big one. Even though I just have Ottos right now, they are sensitive. My rocks leach, I seemingly need more calcium than most, so I can limit the shock I knew my fish were facing, but have a better idea of what is going on.


In comparison, before using one, I just had to guess based on a bunch of fertilizing parameters other people used, while having my own specific problems with plants, while knowing our water is not equal, and only using experience as a guide.

I see my fish more active, and I use a lot more caution. I am seeing more favorable results, and feel I have more to go off, with a very small investment. It doesn't tell the whole story but it definitely tells a story that I can start to qualify, though not exact enough to quantify, I think it is a must have given $20 goes a long way. I imagine I will rely on it less in the long term, like test kits, but it still tells the story when there is a problem.
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post #6 of 9 (permalink) Old 12-05-2019, 12:49 PM
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Having one on hand is really nice. I'm not sure I would have discovered how unsuitable our well water was at our new house as quickly as I did if it wasn't for the fact that I had a TDS meter. At my old house the TDS out of the tap was around 250. Pretty high but we live on top of limestone so it's expected. Moved to the new house and out of the well the TDS was 750... First thing I did was setup an r.o. system lol.

We have so much iron in our water here it's nuts.
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post #7 of 9 (permalink) Old 12-06-2019, 01:02 AM Thread Starter
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I really appreciate everyone's replies. @talontsiawd, should I take this to mean that the higher the tap water TDS reading, the more it should be diluted with R.O. water when doing water changes? Also, can you recommend the specific TDS meter you got for $20? I think I'm going to buy one and put it in my hubby's X-mas stocking, but there are so many models out there and at all price points. I'm not looking to buy top of the line but would hope to get a reliable one. Thank you for your in-depth reply, now at least I think I have a basic understanding of TDS meters and their purpose/necessity.

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post #8 of 9 (permalink) Old 12-06-2019, 04:09 AM
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Quote:
Originally Posted by makeme View Post
I really appreciate everyone's replies. @talontsiawd, should I take this to mean that the higher the tap water TDS reading, the more it should be diluted with R.O. water when doing water changes? Also, can you recommend the specific TDS meter you got for $20? I think I'm going to buy one and put it in my hubby's X-mas stocking, but there are so many models out there and at all price points. I'm not looking to buy top of the line but would hope to get a reliable one. Thank you for your in-depth reply, now at least I think I have a basic understanding of TDS meters and their purpose/necessity.
Please know that I just got one so I am no expert. Check the shrimp forums for brands but I was recommended this on Amazon: HM Digital TDS-3 Handheld TDS Meter With Carrying Case, 0 - 9990 ppm TDS Measurement Range, 1 ppm Resolution, +/- 2% Readout Accuracy

That was recommend for under $20. Is it good, I don't know, but seems to follow what I do, but I haven't even had it for 30 days, I can still return it.

As for the first part, I would say if you want lower TDS, and you have high TDS out the tap, yes, it would make perfect sense to use more RO water. If your RO water is like 3-10, and your tap is 500, then you could do 50/50 and get 250, or whatever makes sense.

For more specifics, I am not the one to answer questions, yet, I don't know enough. I currently EI dose and it seems that can raise the TDS 100-150 before the weekly water change. That is just what I read here. Since that is what I do, I give a range of about 250 before I do a water change, or weekly, whichever comes first. I am experiment as I have a not so common deficiency that I am trying to figure out. Point being, most people use it as a basic assessment or guideline, not scientific, just a bit of information to consider.

I still recommend picking one up, I think it is a great gift idea at the least, but I actually like mine way more than I thought. My water is inconsistent too, that alone helps me. But I had a 14x increase than my tap, I saw a big difference getting it down to 3x as much. I wouldn't have known with any test kit I use, and I don't test my water daily, I test my TDS daily or more, because it is so easy to do. I would check the shrimp forum on the search, it is really important with sensitive shrimp and breading it seems.

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post #9 of 9 (permalink) Old 12-06-2019, 05:11 AM
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Quote:
Next, I found I can have a TDS as low as 20 or as high as 90 out the tap. I don't know why,
Seasonal changes cause changes in TDS. When you add billions of tones of rain water (TDS clos zero) to a reservoir the TDS of the reservoir water has to drop. Alll tap water is treated and filtered at the utility water treatment plant. Home and condos generally don't have any filter unless you install one. Additionally your water utility has multiple reservoirs. Sometimes water utilities shut off a water source to perform maintenance to the water treatment plant attached to it.. During a period of drought more well water would be used which will increase TDS.
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