Can you recommend a GH test kit brand that will measure GH to levels greater than 200 ppm.
GH test kit question
- Thread starter gwand
- Start date
Uberhoust
Fish Herder
The API GH test kit might not give a table over 200 but with it each drop is equivalent to 10 or 20 ppm so in effect you count the drops and there is nothing stopping you from going further. The test accuracy might drop off with more drops, but too much over 200 and you are getting into pretty hard water. I think it would work well enough to determine any sort of dilution rate if you are mixing water.
A test kit that works by drop count instead of color matching will be able to test harder water.
A7830 - Nutrafin Carbonate and General Hardness Test - Hagen
Most liquid GH testers work by titration - adding reagent drop by drop until the liquid in the tube changes colour.
OP
OP
Yes. I use the API system but didn’t know if the drops were proportional in a linear fashion to the GH once the GH reached 200 ppm.
The drops are the same, whatever the GH. 1 drop = 1dGH = 18ppm (approx). 200ppm is about 11dGH, so your test will change colour with the 11th or 12th drop.
TwoTankAmin
Fish Connoisseur
While I have the API GH/KH kit, I prefer to use and have two of these.
https://www.amazon.com/HM-Digital-TDS-3-Handheld-Carrying/dp/B000VTQM70
https://www.amazon.com/HM-Digital-TDS-3-Handheld-Carrying/dp/B000VTQM70
OP
OP
I generally use the Seriously Fish website to begin my study of a fish I may want. The sight reports the tolerable range of water hardness for a given fish in GH. How would I translate a GH range of 150-200 ppm, for example, into TDS metric?While I have the API GH/KH kit, I prefer to use and have two of these.
https://www.amazon.com/HM-Digital-TDS-3-Handheld-Carrying/dp/B000VTQM70
There's no direct, universal conversion factor between GH and TDS...
GH only measures calcium and magnesium ions, while TDS measures all dissolved solids, including salts, minerals, and organic matter.
A rough conversion factor of 0.7 to estimate TDS from GH can be used. However, this is highly variable and should be used with caution.
A TDS of 150 ppm would equate to an estimated GH of 150 * 0.7 = 105 ppm. But the actual TDS value could be significantly different. Correlations and experimentation can provide a ballpark figure that can be used with a specific water source tho.
GH only measures calcium and magnesium ions, while TDS measures all dissolved solids, including salts, minerals, and organic matter.
A rough conversion factor of 0.7 to estimate TDS from GH can be used. However, this is highly variable and should be used with caution.
A TDS of 150 ppm would equate to an estimated GH of 150 * 0.7 = 105 ppm. But the actual TDS value could be significantly different. Correlations and experimentation can provide a ballpark figure that can be used with a specific water source tho.
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MaloK has it the wrong way round. GH measures only dissolved magnesium and calcium, because these are the main ions that cause hardness.
TDS measures the total dissolved solids, which is magnesium, calcium and everything else.
TDS therefore will always be higher than GH.
TDS measures the total dissolved solids, which is magnesium, calcium and everything else.
TDS therefore will always be higher than GH.
Last edited:
TwoTankAmin
Fish Connoisseur
Warning- Science below- 
I do check GH and KH, but I prefer the TDS. Our fish live with everything in their water not just calcium and magnesium. It is important to understand what a TDS meter measures and what it does not.
A good place to start is to look at close to pure water. This would be something like water run through an RO/DI unit or distilled water. This has almost nothing in it beside H2O. What makes water conduct electricity is the other things in it. Pure water is a poor conductor of electricity
There are two differnt common measures used for testing the conductivity of water. Both work in similar ways. There are two elecrodes one sends out a know level of electrical current and the other one measures how much or that current reaches the second probe. The "stuff" in the water besides H and O may be measured.
Conductivity basically measures ions and other inorganic substances and is commonly measured in microsiemens. One the other hand a TDS meter which starts out testing conuctivity but it will also measure disolved organics in the water as well. So TDS is a broader measure.
However, neither comductivity nor TDS provides any information on the specific values of all the different things in the water, For that we would need to sent a water sample to a laboratory which would test for all the individual things contributing to the water many of which are not included in either testing method.
But then neither KH nor GH comes close to doing this. What they do is to give measurement whic can serve as a baseline to which we can compare simil;ar testing at different times or different waters. If one has a decent familiarity of of what is in their water, a TDS meater can tell us how stable that is over time.
I use the conductivity tester I posted above whan I run my bio-farm for cycling filters. What I am actually most interested in is the KH, and I can use my TDS meter for that. The bacteria need inorganic carbon which is what KH basically measures (carnonates and bicarbonates). Because a bio-farm makes high demands for ammonia and inorganic carbon, a serious drop in these will stall a cycle. KH is also what holds pH steady.
So I can test my water in two ways to make sure the cycling is moving apace. One is pH as a notable drop in KH will cause water to become more acid. Also I can use my TDS meter to show me that the KH must be down because the TDS level drops markedly. In our water both as pH and and temperature levels rise, it will increase the conductivity/TDS. Te satandard for measuring the is to test at a temperature of 25C.
Since I keep a fair number of warmer water fish my tanks tend to be kept in the range of 26.6 - 30C. And I run my bio-farm inthat range as well. I also spawn plecos which sometimes need to be put through a dry/rainy season to induce spawning. This is a somewhat long process done over about 10 -12 weeks. I rely on my TDS meter to giude my changeing of the water parameters. The reason I like the HM TDS-3 is that it also measures temp in C. As an American I am an F guy and have charts on the wall translating 1/2 degree increments of C into their equivalent in F.
The other advantage to measuring the TDS is it takes a lot less time to get the readings, I have nor nasty raeagebts to throw out from our liquid tests, not tunes to clean before and after I test. The tester uses a small battery and these work for a long time. The other advanatge to TDS is it rarely requires that one calibrate the meter.
I use on continuous monitor on a tank which reads either conductivity or TDS (I can chose one of different conversion factors to calculate the TDS form the conductivity). The unit also measures pH. Measuring the pH means having to recalibrate thetest probe for this every couple of months and I have testing solutions for 4.0, 7.0 and 10.0. If you have acid water you use the 4.0 and 7.0 and for alkaline water it is the 10.0 and 7.0.
It is one thing to use out KH and GH kits and then either of the two measures above for testing our water. But when we need to know the more in depth measurements of all the things in the water, we must sent it our to a lab and pay a fair amount for this. This is why we are often told to get these test results from our water supplier who is required to do the on depth testing we cannot. But these test are not often preformed frequently the way we can test out tank water using the kits and meters mentioned here.
Depending on what specific level of information we need will determine which is the best tool for us to use. The one thigs for sure is that the more we know the better but also the faster we can get and indication of things changing, the better that is. So I have the API general kit as well as their gh/kh kit.
Salt is one thing neither HK not GH measure but it is captured by conductivity or TDS testing. Salt water is a better conductor of electricity than is fresh water. This is one reason we freshies rarely have a specific gravity tester to determine the salinity of our water that way folks who do brackish or full salt water normally have.
What sorts of methods you use for your tanks is up to you. The inportant part of it all is that you can monitor your water for changes in parameters. If I did not do the bio-farm, did not keep Altum angels and did not do dry.rainy seasons, I likely would not have either my HM TDS-3s nor my Blue Lab Guardian Monitor. I have the one without the Wi Fi as I do not use a smart phone.
https://support.bluelab.com/bluelab-guardian-monitor
Here is a quick table of the conductivity or different waters:
The units might be referenced as micromhos per centimeter (μmhos/cm) and millimhos per centimeter (mmhos/cm) or microSeimens per centimeter (μS/cm) and milliSeimens per centimeter (mS/cm). Thus, 1 mmho/cm = 1 mS/cm = 1,000 μmhos/cm = 1,000 μS/cm.
The above is another reason I prefer to use a TDS meter. I understand ppm a lot better than any of the above conductivity measures.
I do check GH and KH, but I prefer the TDS. Our fish live with everything in their water not just calcium and magnesium. It is important to understand what a TDS meter measures and what it does not.
A good place to start is to look at close to pure water. This would be something like water run through an RO/DI unit or distilled water. This has almost nothing in it beside H2O. What makes water conduct electricity is the other things in it. Pure water is a poor conductor of electricity
There are two differnt common measures used for testing the conductivity of water. Both work in similar ways. There are two elecrodes one sends out a know level of electrical current and the other one measures how much or that current reaches the second probe. The "stuff" in the water besides H and O may be measured.
Conductivity basically measures ions and other inorganic substances and is commonly measured in microsiemens. One the other hand a TDS meter which starts out testing conuctivity but it will also measure disolved organics in the water as well. So TDS is a broader measure.
However, neither comductivity nor TDS provides any information on the specific values of all the different things in the water, For that we would need to sent a water sample to a laboratory which would test for all the individual things contributing to the water many of which are not included in either testing method.
But then neither KH nor GH comes close to doing this. What they do is to give measurement whic can serve as a baseline to which we can compare simil;ar testing at different times or different waters. If one has a decent familiarity of of what is in their water, a TDS meater can tell us how stable that is over time.
I use the conductivity tester I posted above whan I run my bio-farm for cycling filters. What I am actually most interested in is the KH, and I can use my TDS meter for that. The bacteria need inorganic carbon which is what KH basically measures (carnonates and bicarbonates). Because a bio-farm makes high demands for ammonia and inorganic carbon, a serious drop in these will stall a cycle. KH is also what holds pH steady.
So I can test my water in two ways to make sure the cycling is moving apace. One is pH as a notable drop in KH will cause water to become more acid. Also I can use my TDS meter to show me that the KH must be down because the TDS level drops markedly. In our water both as pH and and temperature levels rise, it will increase the conductivity/TDS. Te satandard for measuring the is to test at a temperature of 25C.
Since I keep a fair number of warmer water fish my tanks tend to be kept in the range of 26.6 - 30C. And I run my bio-farm inthat range as well. I also spawn plecos which sometimes need to be put through a dry/rainy season to induce spawning. This is a somewhat long process done over about 10 -12 weeks. I rely on my TDS meter to giude my changeing of the water parameters. The reason I like the HM TDS-3 is that it also measures temp in C. As an American I am an F guy and have charts on the wall translating 1/2 degree increments of C into their equivalent in F.
The other advantage to measuring the TDS is it takes a lot less time to get the readings, I have nor nasty raeagebts to throw out from our liquid tests, not tunes to clean before and after I test. The tester uses a small battery and these work for a long time. The other advanatge to TDS is it rarely requires that one calibrate the meter.
I use on continuous monitor on a tank which reads either conductivity or TDS (I can chose one of different conversion factors to calculate the TDS form the conductivity). The unit also measures pH. Measuring the pH means having to recalibrate thetest probe for this every couple of months and I have testing solutions for 4.0, 7.0 and 10.0. If you have acid water you use the 4.0 and 7.0 and for alkaline water it is the 10.0 and 7.0.
It is one thing to use out KH and GH kits and then either of the two measures above for testing our water. But when we need to know the more in depth measurements of all the things in the water, we must sent it our to a lab and pay a fair amount for this. This is why we are often told to get these test results from our water supplier who is required to do the on depth testing we cannot. But these test are not often preformed frequently the way we can test out tank water using the kits and meters mentioned here.
Depending on what specific level of information we need will determine which is the best tool for us to use. The one thigs for sure is that the more we know the better but also the faster we can get and indication of things changing, the better that is. So I have the API general kit as well as their gh/kh kit.
Salt is one thing neither HK not GH measure but it is captured by conductivity or TDS testing. Salt water is a better conductor of electricity than is fresh water. This is one reason we freshies rarely have a specific gravity tester to determine the salinity of our water that way folks who do brackish or full salt water normally have.
What sorts of methods you use for your tanks is up to you. The inportant part of it all is that you can monitor your water for changes in parameters. If I did not do the bio-farm, did not keep Altum angels and did not do dry.rainy seasons, I likely would not have either my HM TDS-3s nor my Blue Lab Guardian Monitor. I have the one without the Wi Fi as I do not use a smart phone.
https://support.bluelab.com/bluelab-guardian-monitor
Here is a quick table of the conductivity or different waters:
| Types of water | Conductivity Value |
| Pure distilled and Deionized water | 0.05 µS/cm |
| Seawater | 50 mS/cm |
| Drinking water | 200 to 800 µS/cm. |
| Rain or Snow water | 2 to 100 µS/cm |
The units might be referenced as micromhos per centimeter (μmhos/cm) and millimhos per centimeter (mmhos/cm) or microSeimens per centimeter (μS/cm) and milliSeimens per centimeter (mS/cm). Thus, 1 mmho/cm = 1 mS/cm = 1,000 μmhos/cm = 1,000 μS/cm.
The above is another reason I prefer to use a TDS meter. I understand ppm a lot better than any of the above conductivity measures.
OP
OP
I understand the principle behind TDS and all the chemistry issues we face in our hobby. I ran a very active research lab for 40 years. I only saw patients one day a week. Measuring GH in my water to determine what kind of fish I can keep seems much more practical than a TDS measurement. I say this because the websites that I use to purchase fish generally provide the range of GH that the fish will thrive in, not the TDS range. It would appear that measurement of TDS would be more useful for surveilling weekly maintenance of the tank. I assume that between water exchanges if the nitrate level is rising, so will water conductivity and the TDS measurement. This thread started because the API GH kit’s GH table tops out at 200 ppm. So I was not certain whether the pH of my well water was 200 ppm or actually higher. Now from this thread I’ve learned I can keep adding drops using the conversion that one drop equals about 18 ppm.
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