Phosphate Deficiency? - The Planted Tank Forum
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post #1 of 16 (permalink) Old 09-19-2020, 10:37 PM Thread Starter
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Phosphate Deficiency?

Hello everyone - I have been in the hobby for several years but just recently trying my hand at aquascaping and high tech tanks. I think I have gotten my macros and micros at a good levels in my tank but I suspect I’m still having a PO4 deficiency based on seeing dark spots on older leaves. Would love your thoughts to confirm what I suspect. Thank you for your time.

More data points:
Tank ADA 60P - 75 liter
Lighting - Twinstar 600
Photoperoid - 9 hours
NO3 - 20 to 40ppm
K - 20-30 ppm
PO4 - 0.5 ppm
Fe - 0.2 - 0.3ppm
CO2 - 27-33ppm
KH - 3-3.5
GH - 4-5
TDS 140 - 160
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post #2 of 16 (permalink) Old 09-20-2020, 12:39 AM
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Seems like your light and CO2 are in good shape, so a different deficiency seems likely.

I don't see any micros, other than iron, being dosed. Are you dosing them and, if so, what are you dosing, quantity and how often? The discrete brown dots almost look like a severe zinc deficiency (K seems good) and there may be other micro deficiencies involved. Some of the older leaf yellowing may be a Mg shortage. Do you know what you Mg levels are? Are you dosing Mg? Lastly, although I don't think it's a PO4 deficiency, if it were me I would get PO4 up into the 3ppm area for high-tech.

At some point, you may want to take a look at the roots and make sure that they are white and not browning. What is your substrate and how old is it?
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post #3 of 16 (permalink) Old 09-20-2020, 01:55 AM Thread Starter
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Thanks for your reply Deanna!
I forgot to mention that I use Easy Green for my micros. I dosed about 10 ml per week which should give me these levels:
Mg - 0.18 ppm
Zinc - 0.019 ppm

I use Amazonia which is 8-10 months old. I started using Amazonia root tabs about 2 months ago.

Based on my dGH of 4, I’m estimating to have 8-10 ppm of Mg assuming an even split with Calcium.

Last edited by Darkblade48; 09-21-2020 at 03:27 AM. Reason: Please use the edit function for back to back posts to keep threads cleaner
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post #4 of 16 (permalink) Old 09-20-2020, 03:24 AM
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Hi bohemio,

It is highly unlikely that you have an "even split" of calcium and magnesium. On average the ratio is 2 parts calcium to 1 part magnesium but if the water source is well water the calcium levels can me much, much higher depending upon the part of the country and the amount of limestone in the area. If you are on municipal water their water quality report may indicate the amount of Ca and Mg. The amount of Mg can be determined by testing the dGH and testing the calcium ppm and doing come computations to determine the Mg ppm. -Roy

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post #5 of 16 (permalink) Old 09-20-2020, 08:44 AM Thread Starter
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You are right Roy. My Ca and Mg ratio assumption was very wrong. Based on the city’s water quality analysis, my ratio is more like 8:1.
So at 4 dGH, my Ca is about 64 ppm and Mg 8 ppm.

But I read in a different post (https://www.aquaticplantcentral.com/...l#/topics/2427 ) that I need to dive my Ca by 2.5 and Mg by 4.1 to get the real ppm which gives me:
Ca 25.6ppm
Mg 1.95ppm

Just picked up a Calcium test kit and I got about 35 ppm with a GH of 5.

Mg = ( (GH x 17.9) - (35 x 2)) / 4.1 = 0.4

I will raise my Mg to at least 10ppm to get a 3.5:1 Ca:Mg ratio and will report back my results.

Last edited by Darkblade48; 09-21-2020 at 03:27 AM. Reason: Please use the edit function for back to back posts to keep threads cleaner
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post #6 of 16 (permalink) Old 09-24-2020, 01:42 AM
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Hi @bohemio,

Are the new leaves coming in looking healthy, more or less 'flat', with good green color in both the leaf veins and the areas between the veins? Obviously the pictures show older leaves that is why I am asking.
-Roy

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post #7 of 16 (permalink) Old 09-24-2020, 04:22 AM
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I don't understand why the conversation went astray. A PO4 reading of 0.5 is indeed low, besides that the test is not that accurate and the content might be even lower than that. I suggest you definitely keep your PO4 around 2ppm and see how everything develops.
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post #8 of 16 (permalink) Old 09-24-2020, 08:40 AM Thread Starter
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Let me share a mid-week update. I have brought up my Mg to about 10ppm, Ca is 30ppm. GH is now 6-7. I also lowered my nitrates to 10ppm from about 40ppm after a 50% WC, cleaning/trimming/vacuuming and replacing my filter bag with new Seachem de-nitrate rocks.

My phosphates are still testing in the low range 0.5ish ppm. I got some frozen blood worms that should add more phosphates. After I melted the frozen cube with about 20 ml, I tested about 10ppm. I will spoil my tank with more wormz tomorrow and Friday 🙂

My hygrophilia pinnatifidas are looking healthier and the browning and spots seemed to have stopped. My main plant shot 4-5 runners on the sides. The top leaves are getting redder. The plants at the bottom have a healthy green tone. Even my rottala mini-butterflies seem to be recovering after they melted (I attribute it to the high NO3) but that should be another post.

My rotala shimoga still has brown leaves in the bottom 1/3 but I don’t think those leaves will recover. Should I prune them or just cut the stem above the damage and replant?

After raising my phosphates above 1ppm, I will post sn update.
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post #9 of 16 (permalink) Old 10-01-2020, 07:09 AM
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Your Nitrates are high because your Phosphate is low, you shouldn't need denitrifying media in a planted tank. Plants can not uptake Nitrate without Phosphate. But don't go too crazy, 10ppm Phosphate could be too much. I might be wrong but I think I read somewhere that high Phosphate can burn plants.

Once everything gets going make sure to dose Potassium as well, when it runs low you will see holes in old leafs.
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post #10 of 16 (permalink) Old 10-02-2020, 12:52 AM Thread Starter
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Finally getting back with an update. I’m happy to report that my plants are thriving! I brough up my phosphates to 1ppm and that unblocked my nitrate uptake overnight. My nitrates dropped to zero (vanostav61 you were spot on!) and my phosphates to 0.5. My plants were definitely phosphate deficient. I dosed another 1 ppm of phosphate and the uptake has been crazy.

I was starting to see GSA which is now in retreat. My Ludwigia leaves are getting longer and have a great tone. My rotalas are growing again. My crypt stopped melting. Even my java ferns are growing at a fast rate and pearling like never before.

To recap: I ended up having a Mg and PO4 deficiency. It caused stunted growth, higher nitrates, and brown spots.

Lessons learned:
Ensure a Ca:Mg balance of at least 4:1 and up
to 2:1. (Thanks Roy for suggesting this)
Low phosphates will lock nitrate intake, create GSA and stunted growth, spots and browning.
Bring up Phosphates to at least 1ppm.
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post #11 of 16 (permalink) Old 10-02-2020, 01:56 PM
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I wouldn’t be too quick to assume that adding PO4 to a PO4-starved plant is going to result in such a dramatic instantaneous response. I would tend to think that your primary problem was the Mg, as @Seattle_Aquarist mentioned, and a response of several days, which you are seeing, is more reasonable.

Test kits can give a false impression of having too much of any nutrient. So, it is quite possible that you had much less PO4 than your tests showed, as @vanostav61 mentioned. If your PO4, in fact, was at .5ppm, you should be fine but, as many of us mentioned, having it higher in a high-tech tank is preferred. It gets into the EI/unlimited nutrients concept. Low PO4 levels don’t “lock” nitrate uptake, it slows overall growth and, therefore, plants don’t uptake any nutrient as fast as they would with fully unlimited nutrients. Limiting PO4 is a tactic for slowing growth safely and it is quite possible that your slower growth was a combination of both PO4 and Mg, with the low Mg causing the deficiency symptoms that you observed.
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post #12 of 16 (permalink) Old 10-02-2020, 04:41 PM
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When we say "bring phosphates to 1PPM" (or fill in for any PPM target), do we mean that is how much to dose for the week or that anytime a test is run, that's how much surplus phosphate should be detected in the water column at any given time, for example with an API or Lamotte test?
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post #13 of 16 (permalink) Old 10-02-2020, 05:20 PM
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Quote:
Originally Posted by ahem View Post
When we say "bring phosphates to 1PPM" (or fill in for any PPM target), do we mean that is how much to dose for the week or that anytime a test is run, that's how much surplus phosphate should be detected in the water column at any given time, for example with an API or Lamotte test?
We are speaking about the tested levels in the water column, not the dosing amounts.
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post #14 of 16 (permalink) Old 10-09-2020, 07:27 AM
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If old leaves are patchy dark green, is that phosphate deficiency as well? I don't have test kit to test phosphate at the moment. Before I only see this in bacopa caroliniana but now ludwigia sp "dark orange" as well. New leaves on ludwigia are big & healthy but small on bacopa.


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post #15 of 16 (permalink) Old 10-10-2020, 08:29 AM Thread Starter
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Quote:
Originally Posted by kizwan View Post
If old leaves are patchy dark green, is that phosphate deficiency as well? I don't have test kit to test phosphate at the moment. Before I only see this in bacopa caroliniana but now ludwigia sp "dark orange" as well. New leaves on ludwigia are big & healthy but small on bacopa.
Do you have a photo you could share? My tank is still running a little low on phosphates and I can see browning around the tips of my rotala. My phosphate uptake is about 1ppm every 2-3 days. I dosed 2ppm today and will monitor daily uptake.
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