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Hi All - I'm looking through Amazon and seeing iffy reviews on the TDS meters. I don't mind spending a bit if it's reliable.
Any recommendations? Do any of the multiple testers work? Would be nice to get PH as well as TDS, but most importantly just want an accurate TDS for quick tank checks.
 

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It was cheaper because it's purple.
Few reasons it is cheaper, but don't think it's because of the colour!
- calibration is via a small screw which is much more fiddly and less precise than the digital method
- accuracy is +/-3%, rather than +/-2%
- no temperature compensation

The above may or may not be important to you, but for an extra $7, I would really recommend the newer AP-1 model (it's still an absolute bargain at less than $23!)
 

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I had used this HM TDS EZ one for years, and it seems to do just fine.

However, as I've been getting back into the hobby after a five year hiatus with dart frogs, I purchased one of those super cheap sets that included the ph meter and TDS meter. Although the TDS meter agreed with the one I bought from HM, the TDS meter smelled like the kind of black oil they throw on your driveway when they do sealcoating. There is no way that I would dip something that smells like that into my tank, regardless of how cheap it was.

I'd recommend the HM versions. Great value. Nice product.
 

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TDS meters last forever. They are basically resistance - conductivity meters just like any multimeter is. They need calibration once and if they get of then it is because of mineral deposits on their electrodes. If it happens leave them in vodka for few days and they will be like new again. This is why any Home Depot cheap model will do.

And if you worry about calibration then it is easy to check. Need a digital scale and any kitchen salt, here is how, How to calibrate or verify TDS & Conductivity meters?

Probes measuring pH need constant calibration and the cheaper models never work right. And they last only few months to a year or so.
 

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Edward - Any thoughts on a pH meter or two that you would consider decent quality? I have no desire to spend a fortune on testing gear, but it makes no sense to buy a $10 meter over and over and over. In your opinion, what's likely to last the normal 12-18 months and provide decent results? Thanks!
 

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Hi tom855
I am sorry, I don’t know. Tried a few pH probes and it was always disappointing. So now I don’t use any, don’t need one. More important is to know KH and TDS. Why do we need a pH probe. The 1 pH drop method for CO2 is bogus and the pH/KH/CO2 table uncertain. In the moment, the classic drop checker may be slow but doesn’t lie.
 

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Ah, for those of us Excel users, we need to find another way. But, remembering that even a decent probe only lasts 12-18 months, helps to keep the "investment" in perspective. It's needs to work and work well, but obviously doesn't need to cost a fortune to do that.

Thanks!
 

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The Ph drop is far from bogus. This is not about perfect science. Nothing with home aquaria is perfect science. It's about what is going to help in most situations and the ph drop does indicate whether you have adequate co2 is most situations.
I have tried to understand this "1 pH drop" method and wanted it to succeed as we have nothing much to go by in this hobby. Everyone was invited to participate in my thread, I have to mention, you have not.

What I have demonstrated, with references, was that 1.0 pH and 1.4 pH drop may indicate anything between 20 and 100 ppm CO2, depending just on location.

CO2 levels between 1.0 and 1.4 pH drop per location,
20 – 50 ppm CO2 rural
30 – 75 ppm CO2 town
40 – 100 ppm CO2 city

No one is demanding perfect science here, but isn’t this too much inconsistency? If you still want to know more why I call this method bogus, look at Diana Walstad reference:

“I picked 0.5 ppm CO2, a value frequently quoted by scientists, based on Wetzel's textbook*:

"The amount of CO2 dissolved in water from atmospheric concentrations is about 1.1 mg/l at 0 degrees C, 0.6 mg/l at 15 degrees C; and 0.4 mg/l at 30 degrees C." “


If we go by this scientific reference, then 1 pH drop represents 5 ppm CO2 in our aquariums. How is this "1 pH drop" not bogus method?

References
pH Drop CO2 accuracy thread
*Wetzel RG. 1983. Limnology (Second Ed.). Saunders College Publishing (Philadelphia, PA), p. 202.
 

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Hi Asteroid
Yes, this is her presentation of CO2 equilibrium between water and active soil substrate generating CO2 as a byproduct of decomposition. But when she talks about CO2 equilibrium between water and the atmosphere then the CO2 concentration is about 0.5 ppm.


Yes, I understand that, but even after the plants use up the co2 generated from the soil, it doesn't drop below 2ppm. Also in hi-tech tank even with inert sub and typical plant load, bacteria, etc the co2 would still be higher than the equilibrium number especially at the start of the light cycle after plants give off co2.
 

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Asteroid
What do you use as the base pH value of which you chase the 1 pH drop?

Is it aquarium water left sit in a cup for 24 hours with active soil at the bottom? Of course not. It is just the aquarium water in the cup.

The reason why I call the 1 pH drop method bogus is because it is based on CO2 equilibrium between water and atmospheric CO2 concentration which varies significantly. It is like measuring speed and always using different mile.

Even if we don’t go with the scientifically proven CO2 equilibrium in water of 0.5 ppm, we have to accept the widely researched atmospheric CO2 levels. These levels vary so much that it makes the 1 pH drop method impractical. For example, if you have closed windows and running air conditioning you will have significantly higher CO2 air concentration than someone having windows open. This difference will be followed by the 24 hours sitting water for setting the base pH for the method. Also, if you live close to a highway you will get very different result than living next to a park. Like I mentioned above

Aquarium CO2 levels at 1.0 pH drop
20 ppm CO2 rural
30 ppm CO2 town
40 ppm CO2 city

Aquarium CO2 levels at 1.4 pH drop
50 ppm CO2 rural
75 ppm CO2 town
100 ppm CO2 city

So your aquarium CO2 level may be very different than mine even though we have the same pH drop. And that is the problem with this method.
 
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