TDS?

[starsplitter7]

I have always used very basic TDS meters. I know they can be very expensive, but I used a model that was about $20. Easy to use and accurate enough for what I needed.

I used the Hanna EC TDS METER.

Here a few on Ebay with Buy now options at $13.
http://search.ebay.com/search/search.dl ... =32&fsoo=2

This one is $26.
http://www.filtersfast.com/HM-TDS-4-Met ... 0707152154

[chefkeith]

Hi everyone,
Thought I'd jump into the conversation as I've always wanted to get a TDS meter as well. I'm put off by my ignorance of what I will need to do to properly calibrate it. Do you have to do this each time you finish or start to use one of the Hanna TDS meters? Which calibration "stuff" should you get....?
Thanks all!

-Tracey

The Hanna meters are pre-calibrated at the factory. More than likely you should never need to re-calibrate it.

Some other tips-

If you ever use it for testing salt water or very hard water, you should rinse off the meter when your done with it in tap water. This way any residue left from previous tests won't interfere with the results.

If you ever use the meter for checking the TDS of water from fish transportation bags, disinfect the meter immediately after use. Be sure not use the meter as a vehicle to cross contaminate the fish bag water with the main aquarium's water. You'll need to disinfect the TDS meter with a weak bleach water, then rinse with a dechlor solution, and then clean tap water after using it on suspect water, Rinse it well in tap water.

There may be TDS variations due to temperature differences. If you compare the TDS, be sure the water is about the same temperature.

[ulthipster]

Great thanks chiefkeith and starsplitter7. I was getting so confused trying to figure out which calibration solution to buy. One description says to use a calibration solution close to the water to be tested. How would you know this if you haven't used the tds meter yet???? I thought you really had to recalibrate every time you used it. That's a relief if I use a hanna one I prob. won't.

Any specific Hanna chiefkeith? I was trying to find one with the 0-9990ish range but the descriptions got confusing!

Thanks again.

[chefkeith]

HM TDS4 is what I use.

http://www.tdsmeter.com/products/tds4.html


You can probably find one on ebay for about $20.

[Batch]

Okay, I've tested my tanks with my new TDS meter:

Could some of the experts help me with interpreting the results?

Tap water = 162

75g planted tank w/ CO2, daily ferts = 299
15-20% weekly wc NO3 ~ 10ppm

55g Loach tank = 364
25-40% wc NO3 ~ 25ppm

15g very heavily planted nano tank = 669 (yikes!)
it loses ~ 1 gal week to evaporation, I remove 2 gals and put back three weekly, NO3 < 10ppm

1 month old 20H - planted just started CO2 = 328
25% weekly wc only occupants are two rams, NO3 ~10

The nano tank gets a lot of evaporation... I guess I need larger water changes? What about the loach tank, is that too high? I'm not currently experiencing any problems a far as I can tell, but what is best for the long term?

Thanks,
Batch

[Diana]

Most of my 'Soft water' tanks are around 300, the Lake Tanganyikan tank is around 800.

Water that evaporates leaves behind the salts and minerals. Even when you do a partial water change and top off the level keeps rising. You could try topping off with RO, if you want to go to that much bother, or just do larger water changes.

Plant fertilizers also raise the TDS, but as the plants are also using the minerals and removing nitrogen, this seems a fair trade off to me. (I have not asked the fish what they think, but they are often playing in and out of the plants)

[chefkeith]

Okay, I've tested my tanks with my new TDS meter:

Could some of the experts help me with interpreting the results?

Tap water = 162

75g planted tank w/ CO2, daily ferts = 299
15-20% weekly wc NO3 ~ 10ppm

That sounds about right. That's about what my tanks were running when I was adding ferts for the plants.

55g Loach tank = 364
25-40% wc NO3 ~ 25ppm

That does sound high. If you stir up the substrate does the water get cloudy? Perhaps something is leaching in the tank?
If you're not adding ferts and nothing is leaching, then an ideal TDS would probably be around 200 ppm if the source is 160 ppm.

TDS changes should be very very predictable.

From my calculations the TDS is going up by about 8 ppm per day in this loach tank.

15g very heavily planted nano tank = 669 (yikes!)
it loses ~ 1 gal week to evaporation, I remove 2 gals and put back three weekly, NO3 < 10ppm

Are you adding ferts in this tank too? Either that or something is leaching in the water. If you have an iron substrate like Fluorite that will add to the TDS also.

1 month old 20H - planted just started CO2 = 328
25% weekly wc only occupants are two rams, NO3 ~10

That's high also if you're not adding anything to the tap water.

Now I'm thinking that the tap water TDS reading is off. Is the tap water supersaturated with gas? If it is, that can give a false TDS reading. What is the TDS of the tap water if you let it sit for 48 hours to let it gas off?

The nano tank gets a lot of evaporation... I guess I need larger water changes? What about the loach tank, is that too high? I'm not currently experiencing any problems a far as I can tell, but what is best for the long term?

Thanks,
Batch

If the water changes are small then the fish probably won't experience much stress.
Monitor the daily TDS changes in each tank. Also monitor how much the TDS drops after a water change. I'd like to hear your results.

[Batch]

55g Loach tank = 364
25-40% wc NO3 ~ 25ppm

That does sound high. If you stir up the substrate does the water get cloudy? Perhaps something is leaching in the tank?
If you're not adding ferts and nothing is leaching, then an ideal TDS would probably be around 200 ppm if the source is 160 ppm.

Thanks for the feedback. The substrate is sand, and no, the water dosen't get cloudy from stirring it up. I add liquid ferts (seachem) to the 15g and 55g tanks when I do water changes, as there are at least some (okay a lot) of plants in all of my tanks. I guess I need to test that and compare it to the tank water instead of the plain tap water. The 75 and 20H have auto-dosers on them, so they get a small amout 2-4 times a day. I call the loach tank unplanted because all the plants are either attached to wood (ferns/anubias/moss etc) or are in pots with a laterite/gravel substrate. I also have mugbai wood in all the tanks.

TDS changes should be very very predictable.

From my calculations the TDS is going up by about 8 ppm per day in this loach tank.

I'll monitor it daily for a while.

15g very heavily planted nano tank = 669 (yikes!)
it loses ~ 1 gal week to evaporation, I remove 2 gals and put back three weekly, NO3 < 10ppm

Are you adding ferts in this tank too? Either that or something is leaching in the water. If you have an iron substrate like Fluorite that will add to the TDS also.

yes, the substrate is flourite/gravel/soil. (Experimenting a bit with this one).

1 month old 20H - planted just started CO2 = 328
25% weekly wc only occupants are two rams, NO3 ~10

That's high also if you're not adding anything to the tap water.

Now I'm thinking that the tap water TDS reading is off. Is the tap water supersaturated with gas? If it is, that can give a false TDS reading. What is the TDS of the tap water if you let it sit for 48 hours to let it gas off?

I'll try this. Interestingly enough, my pond outside has a reading of 180.

The nano tank gets a lot of evaporation... I guess I need larger water changes? What about the loach tank, is that too high? I'm not currently experiencing any problems a far as I can tell, but what is best for the long term?

Thanks,
Batch

If the water changes are small then the fish probably won't experience much stress.
Monitor the daily TDS changes in each tank. Also monitor how much the TDS drops after a water change. I'd like to hear your results.

I'll update.
Batch

[chefkeith]

Now it all makes sense. When fertilizers are used you need to add that in.

[greenbaron]

HM TDS4 is what I use.

http://www.tdsmeter.com/products/tds4.html


You can probably find one on ebay for about $20.

I found this model (is Hanna = HM Digital?)... but it does indicate a re-calibration for aquarium water is required. It comes with one 20ml pack of the "1382 ppm TDS/KCl solution for higher ppm TDS testing needs such as Aquariums" - is this calibration procedure a one-time thing then?

[chefkeith]

Even though I know nothing about it, a 1382 ppm calibration solution sounds wrong to me. Sounds like it would be calibrating for brackish or salt water aquariums, not freshwater.

Sorry, I don't know the answer right now. I'll look into it later though.

I've never needed to calibrate my TDS meter and probably never will.

I got a monthly water report from my water company that says the TDS is from 110 to 150 annually, and those are about the readings I would get from my meter. So I know my meter has been fairly accurate.

It never occurred to me that these meters could be different and that some meters might need to be calibrated or re-calibrated.

[chefkeith]

Got the answer. No, don't re-calibrate with a 1342 solution.

Hanna Meters are factory calibrated to 342 ppm. That would be perfect for freshwater aquariums.

http://www.tdsmeter.com/calibration_maintenance.html

[greenbaron]

Got the answer. No, don't re-calibrate with a 1342 solution.

Hanna Meters are factory calibrated to 342 ppm. That would be perfect for freshwater aquariums.

http://www.tdsmeter.com/calibration_maintenance.html

Hey, thanks for tracking that down! The info I quoted was from the vendor's site. They also say to recalibrate the meter once a month! I think they want to sell more calibration solution, what do you think
The mfg site backs off on that a bit and just says after "prolonged usage" it "may be helpful" to recalibrate. Ok, got it.
Anyway, I'm going to go ahead and pick one of those up, thanks again for the info!

[Curtis]

To a large degree calibration doesn't matter that much for what we do. If one meter reads 150 and another reads 165 for the same solution for us it doesn't matter all that much. The biggest thing you look for is change in tds from what I can tell when dealing with fish tanks. For example TDS is normally 165 and now it's 205... looks like I need some water changes.... or tds normally is 150 and now it's 190... looks like I need a water change... either way it's the difference that we are going for.... TDS allows us to know how consistent are water is over time without having to do all the chemical tests, it doesn't totally reflect nitrate or ammonia or anything us... but it does let you know the water content has changed.

Since our water and tanks can vary so much, it isn't all that important to compare out tanks when mine might read 165 and yours 150... now 500 compared to 100 is significant but I doubt any of these meters will be that far off calibration.

[greenbaron]

yea... i don't know how much if any drift might occur with these meters... that would be the only reason to re-cal i guess...