Potassium Test Kit - The Planted Tank Forum
 
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post #1 of 7 (permalink) Old 05-01-2014, 12:06 AM Thread Starter
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Potassium Test Kit

Hey everyone. I am dosing EI method in my tank as I just recently got CO2 flowing. My tank has roughly medium lighting and I'm trying to dial in the CO2 to the desired output. I realized that dosing the recommended amount of EI for my size of tank is actually WAY TOO MUCH. Obviously I was looking at recommendations for a high light setup. Now I guess this isn't terrible but I don't want to be absolutely wasting these ferts. So I'm toning down the dosages to still remain in excess of nutrients but not out of hand. I can see that my Nitrates and Phosphates are in excess still because those are the only two test kits I have. Can I assume that K and Micros are in excess as well or would it benefit me to be testing Potassium at the least?
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post #2 of 7 (permalink) Old 05-01-2014, 12:59 AM
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I think K test kits for FW are expensive and hard to find. Not worth it IMO... K2SO4 is a lot cheaper if you are worried about excessive Nitrates and Phosphates.

Really though, the whole point of EI is to have way too much of everything and just rely on water changes to keep things from getting to toxic levels.

Make sure you are calibrating your test kits if you are gonna rely on them to adjust your dosing. I tested my API nitrate test kit on a 10 ppm solution... it reads somewhere around 80-160ppm.
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post #3 of 7 (permalink) Old 05-01-2014, 01:45 AM Thread Starter
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Originally Posted by BraveBuc View Post
I think K test kits for FW are expensive and hard to find. Not worth it IMO... K2SO4 is a lot cheaper if you are worried about excessive Nitrates and Phosphates.



Really though, the whole point of EI is to have way too much of everything and just rely on water changes to keep things from getting to toxic levels.



Make sure you are calibrating your test kits if you are gonna rely on them to adjust your dosing. I tested my API nitrate test kit on a 10 ppm solution... it reads somewhere around 80-160ppm.

Those are all excellent points. I have never calibrated my test kits... I just keep brushing off the thought. If I am truly only needing to dose half of the Nitrogen and Phosphorous that EI recommends to achieve excess levels, do you think cutting K in half would be logical as well? Those test kits for K are definitely costly and hard to track down...
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post #4 of 7 (permalink) Old 05-01-2014, 01:55 AM
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When you add N and P you are also adding K, so keep that in mind when dosing. If you have a lot of N and P you should be good on K as well but A little extra K is always good IMO. I think potassium is one of the most common deficiencies.
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post #5 of 7 (permalink) Old 05-01-2014, 02:12 AM
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Glad to see you are up and running. It takes a bit to get there, for sure.
When I did a set of known solutions to do my calibration , I was pretty shocked. On the API liquids, I got almost the same color on most of the samples. So what I was finding that looked like it was really high could have also been read as only moderate. I'm not sure measuring only a sample or two will tell you nearly as much as doing a full blown test on a range of samples. Pain for sure but it did get me much closer to being able to tell what I have.
I found that I do not need any K2PO4 and only a very little nitrate. My fish food do much of that form. But as I cut back on those two, I found a need to up my potassium by adding Pot sulfate.
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post #6 of 7 (permalink) Old 05-01-2014, 02:36 AM Thread Starter
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Originally Posted by PlantedRich View Post
Glad to see you are up and running. It takes a bit to get there, for sure.
When I did a set of known solutions to do my calibration , I was pretty shocked. On the API liquids, I got almost the same color on most of the samples. So what I was finding that looked like it was really high could have also been read as only moderate. I'm not sure measuring only a sample or two will tell you nearly as much as doing a full blown test on a range of samples. Pain for sure but it did get me much closer to being able to tell what I have.
I found that I do not need any K2PO4 and only a very little nitrate. My fish food do much of that form. But as I cut back on those two, I found a need to up my potassium by adding Pot sulfate.

Yeah I guess we'll see what's going on! I currently have a ton of everything (according to my uncalibrated kits) except for the K which I do not know. However all leaves are formed without holes so I think i should be in excess there too. I was dosing a ton of ferts and didn't even realize it was for HIGH light tanks.
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post #7 of 7 (permalink) Old 05-02-2014, 02:00 AM
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If you are feeding the fish a lot:
Fish food supplies quite a bit of N, P, micros
Fish food does not supply much K, Ca or Fe.

Here is how I alter the EI ratio for a heavily stocked low tech tank:
Monitor the NO3. Dose only if it is going down through the week.
Dose the KH2PO4 the same way as the KNO3:
If I dose KNO3, then dose KH2PO4 (observing the EI ratio between these 2 materials)
If I do not dose KNO3, then do not dose KH2PO4, but dose K2SO4 instead, using the amount that should have been KNO3.

Example slightly modified from EI chart stickied at the top of this forum:
40 - 60 gallon tank (no or little fish food contributing)
1/2 Tsp-KN03 3x a week
1/8 Tsp-KH2P04 3x a week
1/8 Tsp-CSM+B 3x a week
1/16 tsp chelated iron 3x/wk

If the fish food is keeping the NO3 high then dose:
1/2 tsp- K2SO4 3x/wk
1/16 tsp chelated iron 3x/wk

If water changes are keeping the GH in the right range for the fish then do not do anything about GH. If you need to dose to raise the GH make sure you are dosing the right amount of Ca AND Mg, not just one or the other.
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