Can you overdose K? - The Planted Tank Forum
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post #1 of 18 (permalink) Old 03-01-2010, 06:43 PM Thread Starter
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Can you overdose K?

Between the 3 macro's our tanks need, I have an easy way to measure N and P. For K however, there appears to be no quick/simple kit. It has been occasionally suggested to me that I could have a K deficiency. If I were to start dosing more K on top of that which I'm already dosing (KNO3 and whatever K is in Flourish), can I overdose?

Assuming NPK is consumed in consistent ratios, I could calculate my K consumption based on how my N and P drop over time. However, I would not be able to determine whether K is a limiting nutrient. Are there any detrimental effects of having your [K] at 2x-3x the target level?

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post #2 of 18 (permalink) Old 03-01-2010, 08:58 PM
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I'm sure someone smarter than me will have a good answer to this but:

~

Honestly I've never tried measuring NPK in my tanks, one I have to many tanks I'd never have time for the fish and plants, and two I haven't found any tests that get past the general 'ballpark' range that would be affordable. That's one of the selling points of the EI dosing scheme, you overdose ferts all week and then remove them with the big 50% water change that way you don't have to constantly test your water.

~

To answer the question, I doubt you can overdose K unless you get crazy.

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post #3 of 18 (permalink) Old 03-01-2010, 09:41 PM
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Actually you can, anytime I do it my rotala sp. green screams calcium deficiency. Back off a hair on the k, and the calcium issues go away.

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post #4 of 18 (permalink) Old 03-01-2010, 09:49 PM
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How much K (ppm) are your dosing normally and in what amount of water?

Sorry now I'm curious as that doesn't happen to me but then I'm a bit conservative with Ferts.

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post #5 of 18 (permalink) Old 03-01-2010, 11:35 PM
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I used to dose K freely, but then I noticed calcium deficiency in a number of my emersed plants and figured out the problem with some research.
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post #6 of 18 (permalink) Old 03-01-2010, 11:43 PM
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Quote:
Originally Posted by tao View Post
Actually you can, anytime I do it my rotala sp. green screams calcium deficiency. Back off a hair on the k, and the calcium issues go away.
Wow, I guess my rotlata seems to be resistant........I have 50ppm of K+ without issues and I also have actually tested the water for K+, Erik has 100+ ppm in his aquarium that won the overall best of show for the AGA contest with a supposed far more sensitive plant, Ammania, I've grown mor erotlata than I shake a stick at at 40-50ppm.

Bark up another tree.

It cannot be due to K+ or Ca++, I'm not saying what it is in your case, but I do KNOW what it is not. I have a control reference, I also can grow the plants listed without any signs of issues in appearances. So can others.

You also gave no ppm's ranges for K+ or Ca++ for this supposed claim. Always a good way to promote a myth.

Try limiting something, say CO2, then try limiting something else slightly more, say K+, what happens if you add more K+ so that CO2 is now more limiting?

You get stunted tips.
That's just one alternative possibly.
There may be more.
CO2 issues often expressed as stunted tips and is a classic sign.
CO2 is FAR harder to measure well than any nutrient.

K+ for most all the species grown by nurseries is about 200-250ppm in solution they use.

20-30ppm K+ is plenty for most aquariums.
Aquatic plant studies tend to use a 40-50ppm range for non limiting nutrient solutions. See Gerloff 1966.

Also see Liebig's law of the minimum, this explains more in terms of the concept of the most limiting factor.

You must rule out other possible causes to conclude anything. I have because I know this claim was wrong about 7 years ago when someone made the claim.

While what you do may work for you, why it works cannot be correct.
In general, K+ becomes like PO4, it's more salt stress at the upper ranges is plants. So it's higher than 200-300ppm in general.
No need to go that high, but the effective range is pretty dang wide.



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post #7 of 18 (permalink) Old 03-01-2010, 11:46 PM
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Quote:
Originally Posted by hydrophyte View Post
I used to dose K freely, but then I noticed calcium deficiency in a number of my emersed plants and figured out the problem with some research.
Name the plant and name the ppm over a time frame???
How do you know it's a Ca deficiency????



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post #8 of 18 (permalink) Old 03-02-2010, 02:36 PM Thread Starter
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Quote:
Originally Posted by bradac56 View Post
How much K (ppm) are your dosing normally and in what amount of water?

- Brad
I'm dosing about 20ppm once per week (dosing KNO3 for ~20ppm NO3). If plantbrain has 50+ppm [K], then I suppose I could even up mine. Is there a desired level for K? I know [N] is usually kept ~10-20ppm and [P] at ~2ppm.

EDIT: What are the average ratios of consumption of N, P, and K?

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post #9 of 18 (permalink) Old 03-02-2010, 04:30 PM
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Average consumption rates will be dependent heavily on things like light intensity/duration, CO2, plant species type and plant density.

10-30ppm seems fine for most folks for K+, you can go higher without any ill effects on most any species, I'm always curious to test higher levels on speculated "susceptible" plants. Never found any yet.

Here's Erik's tank with over 100+ppm:

http://showcase.aquatic-gardeners.or...=0&vol=2&id=18

Another with 30ppm:

http://showcase.aquatic-gardeners.or...=0&vol=2&id=71

It's very easy to hit such a good sized target with some water changes and dosing thereafter. 10+/- ppm is very easy to accomplish. Hanna makes a decent colorimeter for measuring K+. Lamotte and other test are so so at best due to low precision over the desired range of K+ testing. These can be reduced and diluted to improve the precision, but this adds a few extra steps.

My own tanks have never exhibited any sign of Ca or K+ issues and each time this was speculated, I checked the plants.
I had large stands of Rotala "green" in my 180 gallon for about 6 months, I chose another plant, it grew like mad. Dosing was very rich in K+, about 30ppm initially and then another 20ppm during the week, so about 50ppm added a week.

With some build up, uptake etc this means my K+ sits around 50-60ppm.




Where's my stunted tip growth?
If that is really the real reason in and of itself, I'm game to explain how come I add it, , give specific data points, and post the pictures of the resultants, and no stunted tips.

How is this? Magic?

I no think so........

I'd not worry much about nutrients being too high and simply dose and be done with it, then focus more on CO2, current, and light intensity.

They are a lot more effective for management. Folks focus too much on these slight differences in ppm's or nutrients and think it produces dramatic results.

Rarely is that the case. Light and CO2? Very much so.

I add about 45ppm a week of NO3, 10-15ppm of PO4, 2ppm or so of Fe as proxy for all traces. I also add another few ppm's of Ca and Mg, and K+ as GH booster after water changes.

Nothing special really.
You can tweak to suit and likely should.

If you do get stunted tip growth from adding more K+, I'd look at the CO2 again. Current and adjust, if that does not work, try less light intensity since that will reduce the CO2 stress and you should be able to dose more K+ without the same issues occurring, as well manage everything easier and leaner if you think that is somehow a key.

Plants like nutrients, CO2 etc, I add them, pretty simple stuff really.
I use light to limit/manage growth from there.






Regards,
Tom Barr




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post #10 of 18 (permalink) Old 03-02-2010, 07:30 PM Thread Starter
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Great info plantbrain; and a beautiful DT. I do suspect that my system is CO2 limited for the amount of light I give it (29gal, 2L DIY CO2, 36 watts of T5 for 11 hrs/day). Without any desire to go pressurized (big fan of simpler = better over here), I have some Excel en route. We'll see if that helps boost the plants and reduce the algae.

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post #11 of 18 (permalink) Old 03-02-2010, 07:40 PM
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honestly I think you'd find pressurized much simpler once the initial $ layout and setup/tweak is done. No mixing, messing, just refill the tank every so often. I wouldn't do it any other way

I believe my stance on this issue to be perfectly ambiguous and illdefined and I see no reason to elaborate further.
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post #12 of 18 (permalink) Old 03-03-2010, 02:57 PM Thread Starter
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honestly I think you'd find pressurized much simpler once the initial $ layout and setup/tweak is done. No mixing, messing, just refill the tank every so often. I wouldn't do it any other way
Probably, but I chose planted bc I don't have the funds for a reef.

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post #13 of 18 (permalink) Old 03-03-2010, 03:05 PM
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Quote:
Originally Posted by zachfishman1 View Post
Probably, but I chose planted bc I don't have the funds for a reef.
It's hardly the price of a reef setup, $150 to $200 max and if you build it yourself over time I think I've gotten it down to about $120 by buying the fittings at local hardware stores and waiting for good deals on ebay.

For $185 Greenleaf's "Choice CO2 Regulator" isn't a bad entry level rig or Sumo's "Hallmark" line for $190

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post #14 of 18 (permalink) Old 03-03-2010, 03:33 PM
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Quote:
Originally Posted by zachfishman1 View Post
Great info plantbrain; and a beautiful DT. I do suspect that my system is CO2 limited for the amount of light I give it (29gal, 2L DIY CO2, 36 watts of T5 for 11 hrs/day). Without any desire to go pressurized (big fan of simpler = better over here), I have some Excel en route. We'll see if that helps boost the plants and reduce the algae.
On smaller tanks you have a few management options here.
1. Reduced the light intensity. This makes CO2 management much easier. I'd used wire window screen, and layer it 1-2-3 ... and so on deep inside the light fixture to reduce the intensity, by laying it, it will incrementally reduce light to a decent range without much changes to your existing system, you can raise or lower intensity fairly easily, just horticulturalist do with Shade cloth.
Exact same idea, metal screen is not going to burn etc.

I'd reduce the hours to 9 or so.

2. With DIY, well, that is your Achilles Heel. Best to keep on top of that and change the brew more often, say weekly. Also, consider other reactors for adding it to the tank, I made a great reactor design for DIY back 15 years ago that made about 70-90% of the DIY issues go away on similar sized aquariums.

3. Watch ebay etc for cheap Regs, needle valves, solenoids.
Then look local for a fire extingusher place that refills/sells old refurbished tanks. Well under 100$/maybe 50-80$ if you are cheap and patient.
Don't like it later? Feel it's not worth it?
Put the sucker on a reef forum or sell locally to plant person.
You'll make a few $$ and some profit.

You can do all 3 also.
Excel is fine for a small tank.
I resisted gas tank CO2 for 10 years for my own tanks, but I learned the hard way. I am stubborn.

If simpler is better, then water change then dose and be done with it, reduce light some with screen, maybe 1-2 layer to start with(5-15% reduction), keep up on changing the brew.



Regards,
Tom Barr




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post #15 of 18 (permalink) Old 03-03-2010, 03:37 PM
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Probably, but I chose planted bc I don't have the funds for a reef.
I sell plants and make more than any reef person does per unit $ spent on initial set up. There's simply no way to beat it. Same for fish breeding.

So think in terms of plant dollars, see the Shop and Swap sub forum here, folks easily pay for the CO2 gas back a number of times over.

Just keep an eye open for a gas tank, regs etc for cheap..... they will pay for themselves. Put your cheap thrifty skills to work for you.

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