Should I give potassium? - The Planted Tank Forum
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post #1 of 18 (permalink) Old 04-04-2007, 04:35 PM Thread Starter
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Should I give potassium?



I have a 240G Tanganyikan community setup that is also planted in a low-tech fashion - no CO2, 0.75 W/G. The plants are what you can get by with in a cichlid/catfish tank - Java fern, Echinodorus. sp., Cryptocoryne sp. and so on. They are doing reasonably well, but I'd like to see a little more growth. The tank has been running for 2 years, and I gave fertilizer only ones (Jobe's plant sticks), which resulted in an algae bloom, but no appreciable improvement in plant growth. I am assuming that the plants get plenty of N and P, due to the considerable number of fish in the tank, but might be lacking in K. My amateurish thinking is now to just dose some KCl to see if that would get rid of the deficiency and improve plant growth. I am a chemist and have access to analytical quality KCl, so that's not a problem. But does my thinking make sense at all? I realize this is not exactly the traditional approach to fertilizing a planted tank, but then my setup isn't a regular planted tank either. Any comments, suggestions, or just pure speculation about the usefulness of dosing KCl in my situation would be much appreciated. Also how much I might give if I decide to do so. Details about the tank - and more pictures - can be found at www.fmueller.com.

Many thanks

Frank


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post #2 of 18 (permalink) Old 04-04-2007, 04:40 PM
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Are you using any water additives to harden the water for your fish?

Have you tested the N and P levels?
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post #3 of 18 (permalink) Old 04-04-2007, 04:56 PM Thread Starter
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Are you using any water additives to harden the water for your fish?
I have 10 pounds of crushed coral in the sumps. pH is 7.6 and GH about 8. More details about water additives are here.

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Have you tested the N and P levels?
NH3 and NO2- are of course zero. NO3- is kept low because of a continuous automatic water change sytem I am running. I have never tested for P.

Frank
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post #4 of 18 (permalink) Old 04-04-2007, 05:14 PM
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Hi F, I was going to suggest some fert sticks for the swords but you already tried that. The light green color could indicate a deficiency in NO3. Not too likely with the low light and big fishies. How low was it though? Keep in mind that the Swords are root feeders, so if you cleaned out the substrate they might still show deficiencies even if the water column contains some nutrients. Did the Jobes get digged out? I haven't had problems if I didn't add too many, as long as they were pushed all the way to the bottom, so a couple of inches of substrate would cover them. More isn't always better -- I cut them up into quarters, and add them sparingly.

Another cause of for light green growth could be a lack of micros (Fe, Mn). Depending on your water supply, this might or might not be the case. I would suggest to buy a bottle of Seachem Flourish (not Flourish Trace, or Flourish Excel, just Flourish) and add at a low rate to see if it makes a difference.

Besides that, dosing some K might improve plant health as well.

EDIT -- just read on your website that your water goes through some activated carbon. That will strip it of "harmful metals" (micros) and could be an easy explanation for bad plant growth. Try it without the carbon...


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post #5 of 18 (permalink) Old 04-04-2007, 05:16 PM
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How low is the NO3? If it's low most likely the PO4 is low also. And how about traces?

Dosing any traces?
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post #6 of 18 (permalink) Old 04-04-2007, 07:44 PM Thread Starter
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I am not one to clean the substrate much - certainly not around the plants were I expect any roots to be. I cut the Jobes in bits - 1/4 or 1/2, don't remember which - and put them in the substrate next to the swords. I don't think they were dug up, or at least I didn't see it, and the fronts were a lot smaller then. I did, however, put some bits of the Jobes into the roots of the Java fern that's attached to the background, and they probably leached fertilizer into the water column. I didn't think it would matter much, because I used only like 2 sticks for the Java fern, and I have about 300G of water in the system. It now seems that this caused a bit of an algae bloom - nothing drastic, just a lot more pesky hair algae on the background that I had to pull out manually.

Regarding traces, that is good thinking, and I admit that it hadn't occurred to me that this might be a problem. To give truth the honor though, the carbon block filter should be changed every 6 months, and I haven't done that in 2 years, so by now it's unlikely that it's very effective. Also, wouldn't the crushed coral supply trace elements? Still, I might get myself a bottle of Flourish and try that out.

Regarding N and P, you are quite right, Rex, I should probably check those occasionally just to make sure my assumption is true. However, intuitively I'd say with 50 fronts in that tank plus plenty of other cichlids and catfish, they gotta poop something, and I'll be darned if there isn't some P and N in there

Now about the K, when you guys dose K fertilizer, what kind of concentration are you shooting for? If I knew that, it would allow me to calculate how much potassium I should add. Of course I'd start with a modest amount and increase the dosage if required.

Many thanks

Frank

BTW, Rex - that is some fancy logo your local fish club has, and seems like a hard-core kinda organization judging from your signature
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post #7 of 18 (permalink) Old 04-04-2007, 10:01 PM
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I have no advice for you, only wanted to say NICE Fronts and nice tank!!
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post #8 of 18 (permalink) Old 04-04-2007, 11:29 PM
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Crushed coral will not supply enough of the important traces (iron) to make a difference.

Jobe's sticks in the water column will almost always cause algae because of the urea.

Get some Plantex CSM+B for traces and iron.

Potassium levels are normally around 20 ppm.
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post #9 of 18 (permalink) Old 04-05-2007, 12:18 AM Thread Starter
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Many thanks! That's the information I was after! I'll give that a try.

Frank

Last edited by fmueller; 04-05-2007 at 04:20 AM.
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post #10 of 18 (permalink) Old 04-05-2007, 02:59 AM
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Just put some seacham root tabs under the substrate by your rooted plants.
The java ferns will be fine. And measure CO2 too. It's pretty important for plants.


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post #11 of 18 (permalink) Old 04-05-2007, 03:06 AM
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And measure CO2 too. It's pretty important for plants.
He's not injecting CO2, so it's 3-4 ppm.
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post #12 of 18 (permalink) Old 04-05-2007, 03:41 AM
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Very interesting reading on your site Frank! simply amazing story, wow!

Congratz on the great setup!
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post #13 of 18 (permalink) Old 04-05-2007, 05:30 AM
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I believe that you are using UGJ, I don't think the sword plants appreciate water movement, well, water jets at their roots. could this be one of the problems? Perhaps you can try re-planting them in pots then bury the pots in your substrate to avoid UGJ.

Just a thought.

Your fronts are nice, too blue to be burundis, what are they?
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post #14 of 18 (permalink) Old 04-05-2007, 01:42 PM Thread Starter
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The jets are not directed towards the sword plants, and the current is not very strong. Just to keep debris from settling on the substrate. I don't think planting in pots would help, since the jet's don't actually blow inside the substrate layer, just in the water above it. It's an interesting thought though.

Also, the fronts are definitely burundis, just some really nice ones, not the inbred stuff you sometimes see in the chain stores.

Many thanks for all you comments!

Frank

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post #15 of 18 (permalink) Old 04-05-2007, 02:39 PM
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nicest burundi that I have seen, congra. my fronts look blue-r under dim lights. They turn grayish under bright lights, do you have the same experience?
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