# Total Dissolved Solids (TDS) metering for watching your tank water quality?



## KhuliLoachFan (Mar 8, 2008)

I have a question about TDS meters:

Does anybody use one of these to determine your water quality AFTER it has been in your tank for a week, rather than just to test the output of your RO/DI water system?

In other words, I know it's good to use one of these to measure water purity at ultra-pure levels coming out of either (a) tap water, or (b) outlet of R.O. water systems.

But can you use one of these to track weekly, how fast the TDS are building up in your freshwater tank?

I'm thinking of the AP-1:

http://www.tdsmeter.com/img/selectionguide.jpg

I'm also wondering, if I only had one electronic meter, which is more useful, pH or TDS?

W


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## Zebrapl3co (Mar 29, 2006)

You can but what does the TDS tells you?
Nothing much except that there is a build up of particals in the water. If you have a planted tank, your water could have been drinkable clean and you'll still get 200 - 300 TDS levels. Althernately, it could have been poisonous and still show 200 - 300 TDS levels.

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## KhuliLoachFan (Mar 8, 2008)

I guess I figure that what I could learn is how fast the TDS rises, and then, although I can't see it, I can tell whether or not the water change regimen is helping with overall water parameter stability.

Obviously one should still be testing (dip strips in my case) periodically for nitrite, nitrate, and ammonia. 

I find ammonia testers useless to me since I can smell it before my liquid tests can show me the color.

But what I don't know is, is how much overall "osmotic stress" from TDS is there. Apparently some fish-keepers and breeders pay a LOT of attention to TDS to tell them when they are over-feeding, for example.


W


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## PPulcher (Nov 17, 2006)

TDS will be useful to track the amount of organics in your tank once you know the baseline after your water change. They are also useful if you move fish around from tank to tank, or if you get fish shipped to you - that way you can decide how much acclimation the fish require so they don't suffer from osmotic shock. They won't tell you what the constituents of the water are. You'll need other tests for that.

I think it would be a better general diagnostic tool than a pH meter. I don't test for pH much unless I have a specific reason to, and then I use the liquid reagent kits that do a good enough job, for me. Interestingly, the new Fluval filter unit measures conductivity, which is related to TDS. I think the ad blurb said it was a way to measure water quality and tell when you might need a water change.

There is an RO filter in my future to provide softer water for some fish I want to spawn, so a TDS meter is on my Xmas list


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## bae (May 11, 2007)

I don't think a TDS meter will detect unionized compounds, will it? I thought they measured conductivity in microSiemens, so you could have gobs of organic waste in there and it wouldn't register.


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## PPulcher (Nov 17, 2006)

bae said:


> I don't think a TDS meter will detect unionized compounds, will it? I thought they measured conductivity in microSiemens, so you could have gobs of organic waste in there and it wouldn't register.


Now that you mention it... My understanding is that all TDS meters are essentially conductivity meters, that use a conversion formula to produce a TDS number. That said, I now understand that organics tend _not_ to affect the conductivity much (like dissolving something like sugar in the water) and therefore won't be converted. Hmm. Nitrates (NO3-), nitrite (NO2-) etc would be detected, yes? I guess this is what I meant by organics.


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## bae (May 11, 2007)

I think TDS is too coarse a metric for nitrite and nitrate, given that the TDS of Toronto tap water averages 180ppm +/- 15ppm or so, and the TDS in the tank will vary with evaporation and feeding and any fertilizers, water conditioners and other materials you add. 

I've got a TDS meter that came with a grab bag of aquarium stuff, but I've never used it. PPulcher, If you want to borrow it to experiment with, let me know. You're vouched for by DaFishMan. ;-)


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## juanitow (Jun 21, 2008)

I use my TDS meter as a rough metric for water quality. It's useful when you know how fast the conductivity rises under certain conditions. When the conductivity rises too quickly you know something has gone wrong and you need to change the water. 

It does have its limitations as others have mentioned before: if you are presented a tank of unknown history, the TDS will not tell you any useful information.


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## PPulcher (Nov 17, 2006)

bae said:


> I think TDS is too coarse a metric for nitrite and nitrate, given that the TDS of Toronto tap water averages 180ppm +/- 15ppm or so, and the TDS in the tank will vary with evaporation and feeding and any fertilizers, water conditioners and other materials you add.
> 
> I've got a TDS meter that came with a grab bag of aquarium stuff, but I've never used it. PPulcher, If you want to borrow it to experiment with, let me know. You're vouched for by DaFishMan. ;-)


You might be right Bae, but it might be fun to do some little experiments. I'm curious to see what happens during the course of a week after a water change. I'm glad DaFishMan has got my back. Looks like I owe you guys a cup of coffee 



juanitow said:


> I use my TDS meter as a rough metric for water quality. It's useful when you know how fast the conductivity rises under certain conditions. When the conductivity rises too quickly you know something has gone wrong and you need to change the water.
> 
> It does have its limitations as others have mentioned before: if you are presented a tank of unknown history, the TDS will not tell you any useful information.


Thanks Juanitow. I was reading some material about the new Fluval G filter with the built in EC meter. The essential reason why they say it was included was to detect changes, and then to use other tests to figure out what is out of whack. (discussion is here: http://www.practicalfishkeeping.co.uk/pfk/pages/item.php?news=2274)


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## Chris S (Dec 19, 2007)

I would say a TDS meter really isn't necessary. In my opinion, using an ORP meter would give you a better indication of your water quality. That said, I don't think either is really necessary in your case.


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## Zebrapl3co (Mar 29, 2006)

Interesting, there have been some questions reguarding water quality that have be bugging me for 2 years now.
And that talk about osmotic stress knock one of the piece of puzzle in place for me (er I think, well, I'll eventually find out, but it'll take me 1/2 year of testing and charting see some thing, or don't see something for that matter).
Anyway, now that you guys brough it up. Do you guys feel that "Osmotic stress" is one of those water quality factors that is sitting at par with Ammonia/Nitrite/Nitrate tests. I know from observation that some of my planted tank have high TDS. I consistent test 0 in ammonia/nitrite/nitrate, however, I continuously see stress from my fish if I don't change water every week. It's this mysterious factor that I've been after for 2 years now. I can't seem to pinpoint it what it is.
However, there have been tanks that have a high TDS that I never change water for over a months. The fish seems to be fine though. That's a contradiction there ... so I have to really pay attention to my tds from now on to see if there is any link.
Thanks guys...

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## Chris S (Dec 19, 2007)

It isn't necessarily a contradiction - tds just measures the dissolved solids via EC of the water. What these dissolved solids are is not measured, therefore saying one tank has high tds and another has low does not really give you any indication of what may or may not be stressing your fish. 

It likely has something to do with what is actually dissolved, not so much the level of tds


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## bae (May 11, 2007)

In my Old Fart opinion, it's best to do as many water changes as you can manage, on a regular schedule if that helps, rather than use these often misleading technical indicators of how long you can get away with not changing the water, especially in a tank without a lot of plants to give biological stability. Very especially in a tank with a high to moderate bioload.

That yellowish color you note if you drain your tank into a white bucket, that gets darker the longer you put off a water change, is an indicator of dissolved organic compounds, most of which are not ionic and are not detected by a TDS meter. While no one, AFAIK, has ever really analysed this stuff, in an aquarium it could well include pheromones indicative of crowding, alarm or other stress that are really not good for your fish. Note that even a very uncrowded tank has far more fish per unit volume than any natural habitat. While some of the dissolved organics are benign, many of them aren't. While some fish can tolerate water with a lot of DOC, they all do better in clean water. For one thing, DOC consume oxygen as they break down.

And as has been pointed out, TDS doesn't tell you what's in there. A few ppm of nitrite is quite toxic, yet trying to detect it against a starting tap water of 180ppm, plus increase from evaporation, plus minerals dissolving from substrate, wood and rocks, plus ionic materials in food, plus ions from water conditioners and fertilizers is not very effective. And there are processes that reduce TDS, such as plants and algae taking up nutrients, and bacteria and other microbes incorporating them into their growth.

I'm not clear on what a valid use for a TDS meter would be. Testing a mix of RO or DI water with tap water, maybe, to determine if it's to the level you want. Testing natural waters in the field, to acquire info on a natural habitat. Maybe testing the water of newly shipped fish to compare it with your own, but you know that water is polluted, and you know you should acclimate the fish gradually anyway, right? TDS won't give you a reliable metric for osmotic pressure if it's due to unionized compounds.

In medicine, there's no point in ordering a test if the results won't make a difference in therapy. Old Fart opinion continued: It's better to just do what you know is best for your tank than to introduce a lot of testing that's hard to interpret that can induce you to go against the safe and time tested rule of frequent water changes being the best route to good water quality. Just because it has a digital readout doesn't mean it's giving you the info you want.


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## Chris S (Dec 19, 2007)

I couldn't say it any better.


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## KhuliLoachFan (Mar 8, 2008)

I guess I agree with the Old Fart Opinion, mostly.

The water change thing is exactly right, if you make it frequent, and consistent. I think that consistent water parameters are just as important as clean water parameters, for most species. 

Any "how long can I leave it" experiments are doomed, but I do think, that if you can read a conductivity or TDS meter and see a certain stability, you can't assume there's NO problem, but if you do see a rapid sloping change, you can pretty much guarantee there IS a problem. Probably overfeeding.

Then again, if you think you're overfeeding, you probably are. I am also curious about plants. It seems to me that the more water changes I do, the healthier my fish get, and the more of my plants just rot.

This is changing the subject a bit, but I find, I love my time with my tanks. It's my favourite time of the day. In the morning, feeding and checking all my tanks, and fussing with them until i have to leave for work, and at night, watching my fish, especially the fry, adjusting and checking things, doing water changes, playing with underwater "plant arrangements", etc. 

I think having more meters and stuff is just a way to know more about your tank. I wish there was a really bulletproof "water quality" sensor, but I guess that just doesn't exist.

Anyone got a liquid chromatography system or an inductively coupled plasma mass-spectrometer they aren't using?

W


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## Zebrapl3co (Mar 29, 2006)

bae said:


> In my Old Fart opinion, it's best to do as many water changes as you can manage, on a regular schedule if that helps, rather than use these often misleading technical indicators of how long you can get away with not changing the water, especially in a tank without a lot of plants to give biological stability. Very especially in a tank with a high to moderate bioload....


I don't know. I agree and yet disagree. If we go with "old fart" opinions, some people managed to get a way with changing water once a year. 25 years ago, I used to change water every 6 months. My cichlids even spawn (Birchardi). Although I have to admit that eventually it lead to a complete meltdown and all the fish mysteriously died. I gave up and I walk away from the hoby for some 15 years before I got back at it again. But ever since I got back into the hobby, I've been stuck on a weekly water change schedule. Yes, the fish are healthy, fry mortality is low and I can't stop spawning fish. But the matter of fact it. There are still many people out there that don't change water every week. They do it more like once a month. What is the difference between my tank and theirs? Have my frequent water change caused my tanks to be in a state of 1/2 cycled all these time and it was never fully cycled? Is my filter only partially populated with beneficial bacteria because I continuously keep my water too clean for the bacteria to fully develope? Is my filter running at it's optimal performance or only 1/2 used?

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## KhuliLoachFan (Mar 8, 2008)

It's hard to say. I however, have the perfect system.

Here's how it goes: sometimes I forget a water change, and go from weekly to two, or at the outside, three weeks. Some things get out of whack (like nitrates) and other things get better (plants grow GREAT).

Most of the time, I stick to my weekly water changes. On the odd occasion when life gets in the way, I don't panic.

Try it folks. No need to thank me. 



W


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## DaFishMan (Dec 19, 2006)

"I'm glad DaFishMan has got my back. Looks like I owe you guys a cup of coffee"

You sure do bro, this is happening when ? LOL  

PPulcher first taught me about tds then I also discussed with some discus breeders etc.. Here's what I learned.

Nitrates and TDS are both forms of waste that hamper / minimize growth of fry and juvies. TDS can actually stunt fish, as can high nitrates. 
An experienced discus keeper ( 8 years ) stunted one of her discus juvies unintentionally, simply by raising it in a (well maintained) plant tank. She told me if getting discus for the plant tank, to buy ones past juvie stage, and almost adult size. 

That also leads to a) if you are serious about maxxing fry / juvie growth,
you'll raise them in bare bottom tanks, (yup you could have floating plants etc), also normal substrates would be a collecting point for solids.

Would this stop me from letting my endlers or guppys breed in a full substrate planted tank ? No. I'm not a serious breeder, interested in max turnout in shortest time, or going for any awards. They turned out ok, and for me plants are more of the hobby, the fish feed the plants. The fry will take much longer to grow however, and I risk stunting the fry.

I raised my L dorsigeras (got them as juvies) and I raised them in my plant tank. For the time I've owned them, they appear to be alot smaller then they should be. I don't vac my flourite. My w/c was not frequent enough either. So raising a growout group of juvies in hopes of getting a breeding pair - don't do in a full substrate plant tank. IF my fish are stunted, I've hurt my own chances of getting a happy healthy breeding pair, which will be a disappointment. 

For breeders of any fish, this is also why bare bottom tanks are most popular, whether they are aware of tds or just nitrates - it's very easy to see and remove food waste and poop soon as you see it or a couple times a day etc. TDS will be highest in a plant tank, and in 2nd highest in any tank with a substrate. Small or infrequent w/c, just topping your tank, overfeeding, lack of filter maintenance and vaccing also builds it up. 

Therefore nitrates and tds both impact water quality, tds testers would be handy to any breeder interested in maxxing fry growth. Breeders that are already using bare tanks and frequent vac and w/c would have no reason to monitor tds. (in the tanks at least)

A tds meter about as easy to use a a digital thermometer. (I wish there was a similar nitrate tester but don't feel like shelling out $300. or more for the digital one) Serious breeders, pple raising fry or juvies, or simply those curious about tds would benefit from a tds tester, but many do excellent without one as they are already doing the right things. I'd like one just to compare plant tank to tapwater, or to see if I'm leaving way too much mulm in my plant substrate. Ph test would be good if running c02, breeding certain fish or keeping wild-caught fish, also to test for old tank syndrome which can cause ph crash. Ph also one of the tests that should be done when there's any fish health problem.


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## Chris S (Dec 19, 2007)

Your post is somewhat misleading though. You are explaining them as if they are totally seperate from one another.

Nitrates are but one of many things that TDS actually measures. TDS itself is not a form of waste, but rather a measurement of different "wastes" such as nitrates (but also phosphates, sodium, calcium, etc.). It really is nothing more than an "indication" as to how your tank is doing which is not the same as doing direct tests, such as pH, ammonia or nitrate.

TDS will also not really give you any indication of whether you are leaving too much mulm at the bottom of your tank, as you mentioned. As the name implies, it is only measuring the total solids that are dissolved in the water, whereas mulm is not dissolved.

TDS is essentially just measuring everything in the water that is not water (if that makes any sense!). In that sense, you could unknowningly dump 2 pounds of salt into your freshwater tank, have it dissolve and kill all your fish. Your TDS meter will show you a high TDS, but won't tell you what is wrong. So yes, TDS is accurate in identifying a problem, but just about useless in determining what that problem actually is.

In terms of breeding, well, I don't think I would be bothering to watch the TDS. I'd be more concerned with nitrates and other more specific tests that can actually quantify and identify specific water quality issues.


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## DaFishMan (Dec 19, 2006)

Your post make senses and at same time sheds more detail. I'm no expert, trust me. I soak up stuff I read or hear if I have a personal interest. I didn't really study it further. Good point to mention Total DISSOLVED solids not being mulm. Chances are high though it a plant tank is chock full of mulm, plant detritus and the like, the dissolved organics and other things in the water will be high. That was more the correlation I meant in regards to my plant tank. As I mentioned tons of breeders are very successful without monitoring tds or even knowing what it is. Some don't even test their nitrates either, because they are already doing the right things so don't need to test. Frequent water changes etc that lower the nitrates also lower the tds.

I just know if my dorsigeras or if I get other fish that spawn, the fry would probably be born in a plant tank but I'd be nervous of raising them in there for too long as per what I learned of my friends discus and why.


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## ameekplec. (May 1, 2008)

TDS also includes any and all charged particles in the water, many of which probably will have no bearing on the development of fish, like silicates. 

I think it's misleading to say (at best) that high TDS stunts the growth and development of all fry - perhaps of fry of species that naturally occur in very low conductivity areas (ie parts of the Amazon basin), but what about rift lake cichlids? Do not their fry develop fairly quickly in very high TDS waters?

TDS/conductivity is probably more important in the induction of breeding - changes in conductivity often signal rainy/dry seasons (ie lower conductivity with the start of a rainy season, higher conductivity/TDS the peak of a dry season) and can act as an important environmental cue to adults to either get ready for or to initiate breeding.

Like Chris said, there's more to life than TDS.


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## Chris S (Dec 19, 2007)

DaFishMan said:


> I'm no expert, trust me. I soak up stuff I read or hear if I have a personal interest. I didn't really study it further.


No need to be an expert. If you are interested in the hobby, you are forever learning, which is why threads like these are great.


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