Potassium Test Kit: Good & Inexpensive - The Planted Tank Forum
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post #1 of 22 (permalink) Old 04-12-2019, 08:24 PM Thread Starter
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Potassium Test Kit: Good & Inexpensive

There are very few posted experiences on Google for this Easy-Life Potassium test kit, so I couldn’t find a significant number of reviews to convince me, either way, about the efficacy of this test kit. Turns out that it is quite accurate in the 5-15 ppm range, which is where my target ppm for K is. I would appreciate it if others would confirm my observations, if they decide to try this test kit. The kit is in the area of $20-25 US.

Calibration method:
I used 1 gallon of RO/DI water for each of the six test levels, which are in 5 ppm increments from zero to 25 ppm. For the first series, I added KHCO3 to allow confirmation of the dose via TDS (summing the ppm of K and HCO3) and dKH readings as a cross-check. For the second series, I did the same using KNO3, confirming the dose via TDS (summing the ppm of K and NO3) and Salifert NO3 test. Of course, accuracy of these methods is +/- xx%, but it is reasonably close and was cross-confirming.

The TDS meter was calibrated @.5 conversion factor to 342 NaCl and, using a conversion calculator (https://www.translatorscafe.com/unit...20640%20scale/), I was able to determine the 500 scale level to use for my TDS pen by conversion from the 700 scale which reads the actual summed ppm that can be found in the calculators such as @Zorfox’ or RotalButterfly. Water temp used for TDS readings was 25įC, just to help increase accuracy. Example; 245 mg in 1 gal of RO/DI will have 25 ppm of K and 40 ppm of NO3, for a total 65 ppm TDS. While the @.7 TDS meters will show this, the US-based meters mainly use @.5 conversion factor and do not match the summed ppm of what we see in the nutrient calculators.

The test parameters can be seen here:

Code:
Using KHCO3 
K (ppm)    |    5     |   10     |   15     |   20     |   25     |
HCO3       |    7.8   |   15.6   |   23.4   |   31.2   |   39     |
dKH        |    0.4   |    0.7   |    1.1   |    1.4   |    1.8   |
TDS @0.5   |    9     |   18     |   27     |   37     |   46     |
milligrams |   49     |   97     |  145     |  194     |  242     |

Using KNO3
K (ppm)    |    5     |   10     |   15     |   20     |   25     |
NO3        |    8     |   16     |   24     |   32     |   40     |
TDS @0.5   |    9     |   19     |   28     |   37     |   46     |
milligrams |   49     |   98     |  147     |  196     |  245     |
It is probably a good idea to calibrate each newly-purchased test kit to one or two of the test levels, above, to make sure that the kit is not defective/expired. I did see one comment that a confirmed defective/expired test kit was purchased.

Test adaptations that made for easier and more consistent testing (you’ll understand when you read their directions):

- Rather than using the cotton provided (which is difficult to rip apart in a consistent size), I bought a bag of “medium” cotton balls (which are much smaller than typical cotton balls), cut them in half and placed the base into the test tube cap. I then slowly pour the mix into the cap until it is full. I also allowed about ten minutes for the cotton to become saturated.

- Bought a package of blunt-tipped syringes (~$7) and used the smallest (1 mm) to replace the pipette. This resulted in much easier extraction of the filtered test water.

Discussion:
I found that the colors on the color charts were easily distinguishable at the correct levels. However, you cannot distinguish a difference between zero and 5 ppm and the test color is the same at all levels beginning at 20 ppm and above, despite the color chart showing that 25 ppm should be colorless. Easy-Life acknowledged that this is an issue that they are working on.

Bottom line is that, for me, I am confident in being able to determine if K is at 0-5 or 10 or 15 or >20 ppm. Since it is not possible to distinguish between 20 ppm and all levels above 20 ppm, the test is limited to 5-15 ppm.

SEE UPDATE ON 5/28
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Last edited by Deanna; 05-29-2019 at 02:01 AM. Reason: Adjust
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post #2 of 22 (permalink) Old 04-13-2019, 03:20 PM
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Code:
Using KHCO3 
K (ppm)    |    5     |   10     |   15     |   20     |   25     |
HCO3       |    7.8   |   15.6   |   23.4   |   31.2   |   39     |
dKH        |    0.4   |    0.7   |    1.1   |    1.4   |    1.8   |
TDS @0.5   |    9     |   18     |   27     |   37     |   46     |
milligrams |   49     |   97     |  145     |  194     |  242     |

Using KNO3
K (ppm)    |    5     |   10     |   15     |   20     |   25     |
NO3        |    8     |   16     |   24     |   32     |   40     |
TDS @0.5   |    9     |   19     |   28     |   37     |   46     |
milligrams |   49     |   98     |  147     |  196     |  245     |
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Last edited by Edward; 04-13-2019 at 03:35 PM. Reason: .
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post #3 of 22 (permalink) Old 04-13-2019, 05:07 PM Thread Starter
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@Edward: thanks for cleaning that up!
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post #4 of 22 (permalink) Old 04-13-2019, 10:44 PM
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Where are you purchasing this kit? I can't find a U.S. supplier, or at least none that isn't perpetually sold out of the kit.
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post #5 of 22 (permalink) Old 04-14-2019, 12:08 AM Thread Starter
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Originally Posted by kgbudge View Post
Where are you purchasing this kit? I can't find a U.S. supplier, or at least none that isn't perpetually sold out of the kit.
Pro-Shrimp. They are in the UK. It takes a couple weeks to arrive. Iíve purchased other things from them in the past. They are a good source for aquarium supplies.
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post #6 of 22 (permalink) Old 05-29-2019, 01:58 AM Thread Starter
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UPDATE to OP:

I’ve been testing potassium weekly with this test kit and just broke into my second test kit. I’ve tested K weekly for the last eight weeks and noticed a drift down from above 20 ppm, in the first few weeks, to the 10 ppm area where it has remained steady for about five weeks.

I couldn’t understand why it has not dropped into the 5 ppm, or less, level and remains in the 10 ppm area. I thought that the test kit may have gone bad and that the new one would show it below 5 ppm, indicating the possibility of zero ppm (see the OP for how 0-5 is the same color). However, the new kit also showed 10 ppm (which could actually be in the range of ~8 to ~12 ppm). So, I went through the calibration process – again – as described in the OP and it showed the strong accuracy in the ranges shown in the OP.

Given that I use RO to replace my 30% weekly w/c’s and have not added K in over three months, I should have been very near zero K in the tank for a long time. It then dawned on me that there is potassium in our fish food. In my 29-gal, I add 1.5 grams daily of a combination of Spectrum Thera A+ (multiple sized pellets), Spectrum Optimum flakes, Omega One Veggie Mini Pellets and Hikari Bio-Pure Freeze Dried Blood Worms (I have a very heavy fish load). I have no idea which contains the K or how much, but it is adding at least 5-8 ppm K weekly.

This is a warning to any that wish to try this test kit, so that you account for this possibility in your test results. We all know how fish food contributes to the N, P and trace load in our tanks, but I never though that it could add so much K. It may be that this is why my plants thrived before I knew to add nutrients in the 60’s and 70’s (I could never figure that out – in retrospect).
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post #7 of 22 (permalink) Old 05-29-2019, 02:13 AM
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Quote:
Originally Posted by Deanna View Post
UPDATE to OP:

I’ve been testing potassium weekly with this test kit and just broke into my second test kit. I’ve tested K weekly for the last eight weeks and noticed a drift down from above 20 ppm, in the first few weeks, to the 10 ppm area where it has remained steady for about five weeks.

I couldn’t understand why it has not dropped into the 5 ppm, or less, level and remains in the 10 ppm area. I thought that the test kit may have gone bad and that the new one would show it below 5 ppm, indicating the possibility of zero ppm (see the OP for how 0-5 is the same color). However, the new kit also showed 10 ppm (which could actually be in the range of ~8 to ~12 ppm). So, I went through the calibration process – again – as described in the OP and it showed the strong accuracy in the ranges shown in the OP.

Given that I use RO to replace my 30% weekly w/c’s and have not added K in over three months, I should have been very near zero K in the tank for a long time. It then dawned on me that there is potassium in our fish food. In my 29-gal, I add 1.5 grams daily of a combination of Spectrum Thera A+ (multiple sized pellets), Spectrum Optimum flakes, Omega One Veggie Mini Pellets and Hikari Bio-Pure Freeze Dried Blood Worms (I have a very heavy fish load). I have no idea which contains the K or how much, but it is adding at least 5-8 ppm K weekly.

This is a warning to any that wish to try this test kit, so that you account for this possibility in your test results. We all know how fish food contributes to the N, P and trace load in our tanks, but I never though that it could add so much K. It may be that this is why my plants thrived before I knew to add nutrients in the 60’s and 70’s (I could never figure that out – in retrospect).
I find that you found that much Potassium interesting. As all my tanks are heavy bio-load ( lots of cichlids!) and feeding daily, I imagine mine would be the same.
Im curious about what types of fish you have? I dont think Ive ever seen a post on your fish.

180 g. low tech w/ wild South American cichlids, corydoras eques, and African Congo riverine tetras.
60 g. low tech w/ F1 Alenquer pair /Stendker "Tefe" discus and wild Altum Angels
30 g. low tech w/ Wild Tucano tetras
30 g. low-tech African Biotope
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post #8 of 22 (permalink) Old 05-29-2019, 04:37 AM
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Very interesting results - pretty much everywhere it is written that fish food doesn't have potassium and, apparently, it does.


Yeah, I also wonder, what is the fish population in this tank? Just kind of easier to understand the amount of food by fish population - I've never ever weighted the fish food while feeding... And how many plants in the tank relative to fish?



Also, do you add any fertilizers at all in this tank?
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post #9 of 22 (permalink) Old 05-29-2019, 07:27 AM
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Just donít take the test results too seriously. You may be making the wrong interpretation simply because the test kit cannot read low concentrations correctly.
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post #10 of 22 (permalink) Old 05-29-2019, 01:32 PM Thread Starter
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Originally Posted by Discusluv View Post
I find that you found that much Potassium interesting. As all my tanks are heavy bio-load ( lots of cichlids!) and feeding daily, I imagine mine would be the same.
Im curious about what types of fish you have? I dont think Ive ever seen a post on your fish.
Quote:
Originally Posted by Oso Polar View Post
Yeah, I also wonder, what is the fish population in this tank? Just kind of easier to understand the amount of food by fish population - I've never ever weighted the fish food while feeding... And how many plants in the tank relative to fish?

Also, do you add any fertilizers at all in this tank?
I'm still skeptical, myself, about that much K coming from fish food. I just can't account for it any other way and, as I said, I calibrated the new test kit and also repeated, several times, the test on my tank water. If anyone can challenge this, I’d love to hear about it.

I add urea (2 ppm NO3 equivalent daily), .1 ppm PO4 daily, ever-shrinking traces (except Fe, which was increased) and a little Mg when it drifts lower than ~2 ppm. Interestingly, Ca holds steady at ~8 ppm, which also indicates a fish food contribution in balance with uptake. Gravel is inert, so no GH or KH contribution there. KH is well below 1 ppm.

My current 38-fish load (from AqAdvisor - Intelligent Freshwater Tropical Fish Aquarium Stocking Calculator and Aquarium Tank/Filter Advisor):

1 x Corydoras C079 (Corydoras loxozonus)
1 x Featherfin Catfish (Synodontis euptera)
1 x Oto (Otocinclus vittatus)
1 x Bristlenose Pleco (Ancistrus sp.)
1 x Kissing Gourami (Helostoma temminckii)
1 x Honey Gourami (Trichogaster chuna)
1 x Molly (Poecilia sphenops)
3 x Harlequin Rasbora (Trigonostigma heteromorpha)
3 x White Cloud Mountain Minnow (Tanichthys albonubes)
10 x Cardinal Tetra (Paracheirodon axelrodi)
4 x Neon Tetra (Paracheirodon innesi)
1 x Zebra Danio (Danio rerio)
1 x Longfin Zebra Danio (Danio rerio)
1 x Blue Gourami (Trichogaster trichopterus)
3 x Guppy (Poecilia reticulata)
3 x Glowlight Tetra (Hemigrammus erythrozonus)
1 x Swordtail [Male] (Xiphophorus hellerii)
1 x Siamese Algae Eater (Crossocheilus siamensis)

This is way off the scale, so I wouldn't encourage anyone to match this quantity. Those fish that can outgrow the tank (29 gal), already have. According to AqAdvisor, I'm well over 200% capacity. Also, I don't have any bio-media in my filter, so that would make them even angrier.

Lots of plants, mainly stems, so good cleaning and hiding capability.

Quote:
Originally Posted by Tiger15 View Post
Just don’t take the test results too seriously. You may be making the wrong interpretation simply because the test kit cannot read low concentrations correctly.
As you can see, I calibrated both kits and they both differentiate well between 5 ppm and 10 ppm.

Last edited by Deanna; 05-29-2019 at 01:49 PM. Reason: add
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post #11 of 22 (permalink) Old 05-29-2019, 04:00 PM
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Nice balancing act!

While you are over 200% fish load capacity, no bio media and still must be adding 2 ppm NO3 equivalent daily? Something else is eating it up, not plants.

Considering this low Ca of only 8 ppm (1 dGH) and Mg 2 ppm (0.5 dGH), the K requirement is also very low. Most likely still leaching from plant tissue. The assumption of K source from fish food is valid, though very small amount.

How well can you tell the difference between 0 and 5 ppm on the K test kit?
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post #12 of 22 (permalink) Old 05-29-2019, 05:51 PM Thread Starter
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Nice balancing act!

While you are over 200% fish load capacity, no bio media and still must be adding 2 ppm NO3 equivalent daily? Something else is eating it up, not plants.

Considering this low Ca of only 8 ppm (1 dGH) and Mg 2 ppm (0.5 dGH), the K requirement is also very low. Most likely still leaching from plant tissue. The assumption of K source from fish food is valid, though very small amount.

How well can you tell the difference between 0 and 5 ppm on the K test kit?
As you probably recall, I've been doing a steep dive on the nutrients for about 6 months now (and still headed lower on the traces). What else could possibly be consuming the N products other than the plants (and loss in w/c's)? For several months, now, I've been testing at ~5 ppm NO3 AFTER each w/c. The only BB consumption (other than surface coatings) is going to be in the substrate, but my pH is below 6 and bicarbonates are almost non-existent, so how active can the BB be? I have ~2 inches of inert CaribSea Peace River on top of an inch of inert CaribSea Sunset Gold (sand). I can't imagine there is enough anaerobic BB down there to have much of an effect on the NO3 portion. I will say that my plants, which I thought already looked pretty good, looked even better after starting the urea 3-4 months ago. Stem plants became fuller and more colorful (reds may be from occasional bouts of too little NO3).

Yes: I think overall demand is somewhat balanced, i.e.; I'm not forcing the plants to want to suck-up more of anything because I'm not pushing any of the separate nutrients (maybe heaviest on the NH4). Nor do I see any evidence - yet - of any deficiencies, but I'm wondering how far plant reserves can actually go as it has been a solid 3-4 months of withdrawal.

I'm going to try putting a gram or two of my fish food in some RO water and see if I can detect any leaching of PO4, K and Ca over time. Animals need some K, but probably not nearly as much as I'm dosing in their food, so they must be expelling enough to satisfy the current plant requirements ...again, unless I'm still running down the reserves.

Regarding the K test kit: I can easily distinguish between 5 ppm and 10 ppm and between 10 ppm and 15 ppm, and then between 15 and 20 ppm. However, at the 5 ppm indicator color, you cannot know if it is 5 ppm or 0 ppm and at the 20 ppm level you cannot know if it is 20 ppm or any level higher than that.
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post #13 of 22 (permalink) Old 05-29-2019, 06:45 PM
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I've been having what looks like potassium deficiency for a month or two now, and the only way I've been able to get my tank to bubble was by what I thought was overdosing potassium sulfate to get the levels up. Hence interest in actual potassium testing.

Edit: the below was wrong. See the posts after.

I just received the easy life potassium kit and tested straight away. The first time, the liquid in the tube was dark green and the end result was light green. This couldn't have been right as that shade isn't on the results colors anywhere, so I retested and made sure to shake the reagents well and set a timer for 6 minutes exactly. This second time, the liquid in the tube looked like the color and shade of 0 ppm, and the end result matched the shade for 20ppm.

20ppm.... after I've been dosing 1/8 tsp of potassium sulfate daily for weeks. That's around 8ppm of potassium daily. I thought someone mentioned that plants barely use potassium and that even a 1:1 of nitrate:potassium was "just because it's easy and potassium nitrate gets you there anyways". I started this dosing after I realized I wasn't adding any potassium due to not needing to add potassium nitrate. Fish poop and food was enough to get the nitrate to 20ppm~.

So... either plants use much more potassium in a high tech tank than people think, or something else is absorbing it. A near 1:1 ratio of nitrate:potassium is actually important, not a side effect of a simple EI dosing method.At least now I don't feel bad for dumping potassium sulfate into my tank. I aim for 20ppm nitrate, 20ppm potassium, 5ppm phosphate, 70-100ppm of calcium (due to rocks) , 10ppm of magnesium, and .25-.5 of iron.

Last edited by Ddrizzle; 05-29-2019 at 09:42 PM.
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post #14 of 22 (permalink) Old 05-29-2019, 07:13 PM Thread Starter
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I just received the easy life potassium kit and tested straight away. The first time, the liquid in the tube was dark green and the end result was light green. This couldn't have been right as that shade isn't on the results colors anywhere, so I retested and made sure to shake the reagents well and set a timer for 6 minutes exactly. This second time, the liquid in the tube looked like the color and shade of 0 ppm, and the end result matched the shade for 20ppm.
See the OP: if you are getting a reading of 20 ppm with the K test kit, it doesn't mean that potassium is 20 ppm. It means that it is a MINIMUM of 20 ppm. It could be very much higher and still show as 20 ppm. The test kit is only accurate between 5 and 20 ppm.
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post #15 of 22 (permalink) Old 05-29-2019, 07:46 PM
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See the OP: if you are getting a reading of 20 ppm with the K test kit, it doesn't mean that potassium is 20 ppm. It means that it is a MINIMUM of 20 ppm. It could be very much higher and still show as 20 ppm. The test kit is only accurate between 5 and 20 ppm.



Interesting. I'm making a batch of 50ppm in some RO water to test now.
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