How to use a TDS or conductivity meter

[Carol_Roberts]

Discus can be kept in a wide range of pH and hardness.

Hatching discus eggs is another matter. Water has to be fairly soft and pure or the eggs will harden after they are fertilized. Soft water has less disolved minerals like calcium and magnesium. In other words, less Total Disolved Solids or TDS.

Some hobbiests are blessed with naturally soft water, but others of us have to mix Reverse Osmossis or RO water with our tap water if we want eggs to hatch.

How can you tell if your water is soft enough? One way is with a conductivity or TDS meter.

Water conducts electricy based on the amount of disolved solids. Higher TDS = higher conductivity

This simple to use, battery operated meter measures the electrical conductivity between two metal points. A number is displayed on an LED screen.

Most breeders like to keep their water between 80 and 100 ppm.

A TDS meter is more accurate and easier to use than counting drops in a test tube.

Pictures really help me understand equipment. This is the meter. My 13 week old PBxRT are in the background.

[Carol_Roberts]

This view shows the little electode things that measure the conductivity

[Carol_Roberts]

Here is how you take a reading. Just stick it in the tank to the line and press a button

[Carol_Roberts]

Here is the LED reading. You can see it is 276 in this juvenile discus tank - too high for hatching eggs.

[Carol_Roberts]

Then you just wipe it off and put it back in it's carrying case. Every six months you can calibrate it by dipping it in a special salt solution that is exactly 500 ppm. The calibrating solution is not very expensive.

[Anna Piranha]

Hi Carol,
Thanks for posting this. It takes the mystery out of the meters!

- Anna

[Barb Newell]

Hi Carol, thanks for the great post! Mine meter is on its way.

Barb

[brewmaster15]

Great Post Carol!!! keep them coming!!! :)

-al

[Ardan]

8) article


I like the fish too! When you say PB X RT, what is that , Pigeon Blood crossed with ??

Thanks!

[Carol_Roberts]

RT = Red Turquoise

[dm]

I have one and love it. Now I just need to get a hand held pH meter.

[RandalB]

Carol,
Just FYI, you have to use the little screwdriver in the case to adjust the calibration when the time comes. There is a little plug on the case of that particular meter that covers the adjustment screw.

That's why I went to the Hanna Primo's they auto calibrate and you don't have to hold the button down to take readings. The Sprite's are great meters though accurate and low cost. Let me know how that one works out for you and when you need solution.

Regards,
RandalB

[gary1218]

Carol,

I LOVE all these informative articles you've been posting here. Even and old guy like me is learning new stuff ;D

I'd be very curious if somebody had both a TDS meter and a conductivety meter what readings you get if you measure the same water with each different meter.

The reason I say this is that I've read from more than one so called "water expert" that the conductivety meter is the way to go. That the TDS meters don't really measure what you think they do. There was a good article about it in TFH "way back when". Maybe I'll have to dig it out.

GARY

[RandalB]

Gary,
Not to steal Carol's thunder, hand held TDS meters measure conductivity and do a calculation to arrive at TDS. Usually dividing by 2. A true TDS meter is very expensive. The Hand held ones give you an aproximation that is pretty accurate. So they are both Conductivity meters. You'd take your reading and multiply it by the dividing factor for that particular reading (some are .5 some are .65 and some are adjustable for water content) to get your conductivity reading.

It's a matter of personal preference as the meter is almost always measuring conductivity anyway.

I am expecting a shipment of Hanna instrument's DiST 5's which measure and display Conductivity,TDS and temp. I'll let you know what the difference in readings is when they come in.

HTH
RandalB

[Ralph]

Great thread, the photos make it so much easier to understand.

[GulfCoastDiscus]

Hi Carol,
Was wondering where I can purchase the calibration liquid. I've had mine for years and have never calibrated it. Thank you

Dan

[jim_shedden]

Randall :I have a question regarding the Primo you had sent me. When I put it in the water it registers 55 then quickly jumps to 110. What is the correct reading?

Jim

[CARY_GLdiscus]

;D nice write up! ;D

[RandalB]

Jim wait 30 seconds or so and that should be the correct reading.

RandalB

[Carol_Roberts]

I get my calibration fluid from RandalB

[ladyram]

This post is great Carol, but how do I calibrate my tds meter, since I think I did something wrong since I have a figure of 714

[Carol_Roberts]

We'll let RandalB answer that for you

[RandalB]

Ladyram,

Turn the TDS meter on, then push the button again and hold it until CAL appears in the display. Then put the electrode into the solution about half way between the Min and Max markings and hold it there until the display stops flashing and reads 1382.

HTH,
RandalB

[ladyram]

Hi Randall, it's Alicia........you send me the TDS meter with the RO unit a primo

[RandalB]

I know now. I really should read profiles before I respond to posts. See my above post...


RandalB

PS: Your Fittings are on the way...

[ladyram]

Great!!!! It worked Randall and I think is calibrated now, but the figure is still 714 ¿¿is that too high?? ¿¿or I am still doing something wrong??

[RandalB]

Which Figure is that? Your RO water or Tank water? If it's your RO water it's too high. If it's your tank water it's possible. What's the reading on your feed water?

RandalB

[ladyram]

This figure is of my tank, I haven't installed yet the RO since I need the fitttings and an hour from my husband, hehehe.

Alicia

[RandalB]

Alicia,
What's the reading on your tapwater? Do you use any buffers?

You can run your RO unit w/o that Fitting, but I can't help you with an hour from the husband... ::)

RandalB

[ladyram]

the reading in my tap water is 456, I don't use any buffers at all, I only use peat granular in my filter and a softener pillow, and I age my water for 24 hours aprox.

I use to make 30 to 40% wc daily.

I made some tests on my tank and aged water and were as follows:

tank
PH 7.8
GH 15 (last friday was 30 :o)
KH 5 (last friday was 3)

Aged water
PH 8.4
GH 15
KH 4

[RandalB]

Alicia,
Your TDS could get to the 700's no problem with the feed water being so high. Biological activity can drive TDS up pretty quickly.

RandalB

Randal,

Its the water soften pillow that she uses. They exchange calcium and such with salt and drive up the conductivity.

Let me know if I am wrong?

thanks

mattd

[Ardan]

Carol,
Can you please post your pics again if you have them?

Thanks
Ardan