Can zinc be a problem?

[HiNtZ]

I don't see a lot of discussion about zinc on the forums and am curious if anyone has any info on it, specifically why commercial ferts use such dramatically different amounts to each other, especially in relation to boron.

As an example, APF trace mix vs CSM+B (I use the former but will be trying the latter from next week).



Looking at the other elements such as Cu & Mo there appears to be 2-3 times more in APF than CSM+B?

I've always had adverse effects using APF stuff in soft water (6GH), though never in hard (12-14GH). It seems even a 1/10th dose burns and stunts my plants.

If I don't fertilise, things get gradually better until I hit deficiency. So this must be a ratio issue? Boron perhaps having something to do with it, or, lack thereof?

Any advice?

 

[Ueroe]

could you share what your final goal with these zinc?
for aquascape or for fish pond?
in case for aquascape, i'm quite sure if 95% about C, H, O. 4.9% about N, P, K. and 0.1% regarding Fe, Cu, Mg, Mn, Mo, Zn, etc.

 

[Simon Cole]

I feel very much the same way that you probably do about these metals. The truth is that whether we like it or not, availability and toxicity is highly dependent upon both pH and adsorption. People often concentrate on the former variable, and it is true that even the slightest pH swing can trigger acute toxicity. However, the biggest changes occur when we have high concentrations of these metals adsorbed in our substrates, perhaps to aluminium oxides or humic matter. When those bonds break all at once the effect has greater magnitude. An ammonia spike is one occurrence that will cause water to become acidified. I have lost many hardy plants that can tolerate broad pH ranges due to the ensuing toxicity - caused by a sudden dump of metal ions. The safest strategy in my book is to completely eliminate micro-nutrient/trace dosing until any possibility of an ammonium spike has been overcome. Now that seems a bit silly, because many products like ADA Amazonia are designed to release some ammonia and the established orthodoxy for fertilisation is to dose from the start. After all, we might expect continual fluctuations in our tanks for a number of months as various nitrogen cycling processes ensue... but this is also precisely the problem.

You asked specifically about zinc, and this is a prime example where pH and the rate of adsorption can have a drastic effect on plant growth. Up to about 10 ppm there is no toxicity in the majority of species. The general chemical species under varying pH conditions are shown below:


In a terrestrial soil, the general assumption is that zinc availability drops off when we reach higher pH, something like this example:


These ideas are nothing new. Plants can use certain chemical species of zinc. But when we look at the adsorption of zinc, we get studies that show data like this (Degryse et al. EJSS 2009) :


The key point here is that the relationship of adsorption and availability is both very correlated and very extreme. If I had double the volume of substrate, then I would get double the volume of adsorption, and double the quantity of these ions released if there was a drop in pH. If I had less inert substrate, perhaps I would have less to worry about, but wouldn't I feel that my plants could not feed through their roots, or that there was not a sufficient backup load of nutrients available at their disposal. It becomes a very tricky question. Moreover, we are dealing with multiple plant species, varying soil adsorption rates, and multiple chemical species - that all have varying toxicities. Even with RO water, the job of avoiding toxicity would be difficult enough. Perhaps the future of dosing will be to have a thorough understanding of the chemical adsorption of each substrate and it's depth. We often look at the cation exchange ratio as a method of approximating this number, but what we really need is some serious chemical testing of all of the most popular aquasoils - and a good guide of the micro dosage rates, as particular pH ranges.

 

[dw1305]

Hi all,

I've always had adverse effects using APF stuff in soft water (6GH), though never in hard (12-14GH).

That definitely sounds like a toxicity issue, as @Simon Cole says zinc (Zn) is a lot more available at low pH levels, and a fall in pH could lead to formerly insoluble zinc compounds, in the substrate, releasing soluble Zn++ ions back into the water column.

The issue with a lot of the micro-elements is that the difference between optimal and toxic levels can be vanishingly small.

If I don't fertilise, things get gradually better until I hit deficiency.

That would be my suggestion for the way forward, it isn't very scientific, but it it should work. Just don't add the trace element solution on a regular basis, wait for the start of deficiency symptoms.

It doesn't matter what the deficiency is you just add the micro-element solution, and wait a couple of weeks. Waiting a couple of weeks allows the plant to make use of the non-mobile plant nutrients, which are boron (B), calcium (Ca), copper (Cu), iron (Fe), manganese (Mn), sulphur (S) & zinc (Zn).

With micro-elements, if we ignore toxicity, the difference is really between "none" and "some", you just need "some", the actual value is largely irrelevant unless we add too much and toxicity beckons.

cheers Darrel

 

[HiNtZ]

Thanks guys

I have inert sand but it sounds like I could get a significant amount of residual still in/on the substrate? Should I run some carbon for a while perhaps?

Other parameters are:

7.3GH (Ca 40, Mg 8.4, Cl 35, S 16)
3KH (from KHCO3 + MgCO3)
7.2ph (6ph with CO2)
EI daily macros (3.2ppm NO3, 0.6ppm PO4, 2.3 K)
24c
TDS 180 (week start) 250 (week end)
Profito as trace, half dose. It's the only commercial fert that I can easily get hold of that keeps things from going completely to pot.

Flow/filtration/light and CO2 are on point too so it has to be one of the metals screwing things up.

 

[Simon Cole]

When we talk about mobility of a nutrient, we really mean the efficiency at which mineral nutrients which can be redistributed within the plant. Immobile nutrient deficiency occurs in the newer leaves, and visa versa. In the water column these metal ions can move pretty freely when the become available. Zinc will achieve about 84% removal using activated carbon. Copper and cadmium will achieve 90% and 88% removal using activated carbon within the first 30 minutes. For sulphur, the chemical reactions are a little bit more confusing, but there is some removal and to be honest I doubt toxicity that likely. For manganese, we are looking at about 90% removal within 30 minutes using activated carbon. Boron removal is a bit more difficult because the adsorption capacity is rather low (0.59 mg/g). Some studies have indicated that combining the activated carbon into a range of composites is more effective at enabling the removal of boron. My favourite would be an iron oxide-activated carbon composite for this purpose, but there are even examples in academic literature of turmeric being used. If you had a few hours and were scientifically minded, you could have a go at making one of these composites. That is, if you were worried about boron toxicity. You mentioned this also, and I was reading some interesting information on boron earlier:

"Boron is a plant micronutrient peculiar in two respects: (1) its mobility varies markedly among plant species, and (2) the range of tissue concentrations spanning from deficiency to toxicity is narrow...
In species in which boron moves mainly in the xylem sap it accumulates and concentrations increase as the foliage grows older. In those species in which at least part of the boron in the foliage is retranslocated through the phloem to other tissues (e.g. roots, inflorescences, seeds, etc.) its concentration in the foliage tends to remain constant (see Brown and Shelp 1997). When there is B retranslocation through the phloem, it depends on the formation of complexes with sugar alcohols such as mannitol, sorbitol, and possibly pinitol (see Brown and Shelp 1997). Recently B-sorbitol and B-mannitol, and also B-fructose complexes have been demonstrated to occur in the phloem sap of B-retranslocating species (Hu et al. 1997). Further evidence of the importance of sugar alcohols was obtained from transgenic tobacco plants, in which the induction of sorbitol formation gave the new ability to mobilize B within the plant (Brown et al. 1999). Given a long leaf life span (e.g. as adaptation to low availability of a mobile macronutrient such as nitrogen), optimal use of B when availability is low, or toxicity avoidance when availability is high, should favour individuals with the ability to redistribute B away from ‘old’ foliage and towards growing tissues. However, boron retranslocation is not the only strategy that may have evolved in plants for coping with low or high B availability: grasses have very low B requirements (Dugger 1983), and other species like sunflower can tolerate high B concentrations in their tissues using an unknown mechanism to avoid toxicity (Dannel et al. 1999). However, conifers like most species with long lived foliage have woody tissues which require B for their structural integrity."

The point made above is that boron has highly variable results on plant growth generally speaking, and very little is known.
Now coming back to your pH range - your tank varies around maximum micro-nutrient availability for the majority of trace elements. You might expect 12 times the concentration of hydrogen and hydroxide anions as your pH swings, meaning that many trace metals could quite literally break their existing hydrogen bonding (in the substrate - not likely in your case) and eventually enter plant tissue in a protonated or de-protonated state. This situation is quite common as carbon dioxide levels change. Darrel is absolutely right - just add traces when you need them. I think that the only exception might be iron. Iron stress (toxicity) is sometimes desirable if you want redder plants. Conversely, it is also suggested that low nitrogen level enable this. This is probably too due to a inverse increase in enzyme production (for free radical immobilisation) when there is insufficient plant mass/growth. I might be tempted to add just iron as opposed to the complete micro-nutrient trace mix - as many people feel that iron is the key to good plant growth and colour. I think activated carbon is one of the best suggestions I have ever read for dealing with trace metal toxicity (excluding boron). Good idea. Perhaps you might go for the minerals with the lower boron dose. I would also say that the biggest revelation for me is to add activated carbon as soon as you notice a sudden abnormal pH swing or have an ammonia spike. It could save your plants.

It is strange that you are having this problem on an inert substrate. But if we think about the power of adsorption to form reasonably strong bonds - you simply do not have enough adsorption versus the nutrient loading (dosing). Sand forms very few chemical bonds with metals due to its low surface area, impermeable grain, and silicon bonding.

 

[Zeus.]

Very informative guys, one to bookmark/watch for future reference

 

[HiNtZ]

Darrel is absolutely right - just add traces when you need them. I think that the only exception might be iron. Iron stress (toxicity) is sometimes desirable if you want redder plants. Conversely, it is also suggested that low nitrogen level enable this. This is probably too due to a inverse increase in enzyme production (for free radical immobilisation) when there is insufficient plant mass/growth. I might be tempted to add just iron as opposed to the complete micro-nutrient trace mix - as many people feel that iron is the key to good plant growth and colour. I think activated carbon is one of the best suggestions I have ever read for dealing with trace metal toxicity (excluding boron). Good idea. Perhaps you might go for the minerals with the lower boron dose. I would also say that the biggest revelation for me is to add activated carbon as soon as you notice a sudden abnormal pH swing or have an ammonia spike. It could save your plants.

It is strange that you are having this problem on an inert substrate. But if we think about the power of adsorption to form reasonably strong bonds - you simply do not have enough adsorption versus the nutrient loading (dosing). Sand forms very few chemical bonds with metals due to its low surface area, impermeable grain, and silicon bonding.

I've read quite a few posts on various forums over the years about the red plant debate, and how to get them redder. I was doing standard EI (with that APF trace mix) in the hard water tank in the beginning and all my green plants turned pink which was nice. I've never been able to recreate those effects with the reconstituted water and EI anything under 10GH. Very frustrating. I was running silly bright light back then too so always suspected that the light might also be a factor along with N and Fe limitation - but, could this be anthocyanin working here too as a defence mechanism against leaning out on nutrients to protect from the still high light?

I've always been good with my iron (apart from the times I tried none at all) it just doesn't seem to get assimilated efficiently which made me think toward other metals that have a relationship with Fe. Since I show very acute symptoms of Ca deficiency when the trace dose is high, I suspected B (or the B/Zn ratio) might have something to do with it but that's about where my knowledge stops to investigate further. I only go by what I've read.

PH remains stable both night and day, always hits the target and stays there.

I'll order some activated carbon, 90% water changes over 3 days for a nice detox then start with 1/5th CSM+B trace dosing with full EI macros and see if the reduced Zn in that might show some results.

Thanks for the information and help, all of you.

 

[dw1305]

Hi all,

could this be anthocyanin working here too as a defence mechanism against leaning out on nutrients to protect from the still high light?

Anthocyanins would definitely be produced, as a defence mechanisms, if the plant is in high light.

Lower levels of nitrogen would make the plants appear redder, because the red pigments would be less masked by the chlorophyll, but it would be difficult to find the "sweet spot" where there was enough nitrogen for healthy growth.

cheers Darrel

 

[HiNtZ]

So here's an interesting development. I dumped in 30 pumps of some Flora grow pro special fertiliser (colombo) in the tank this morning before lights on and looking now at midnight my rotala has sprouted out an inch from each node! Leaves are plumper too! There are new roots forming also which was always an issue with all plants.

I'm running full brightness 140w LEDs (150L) and elevated CO2 so daily observations can be made on the faster growers. The baby tears is actually sending runners out. It's been in a stasis for months, not doing anything. When that starts growing I know something is right.

So - this is clearly a trace issue, at least for me and for whatever reason. And more specifically APF trace.

This is what's in the Colombo

View attachment 121361 View attachment 121362

So zinc seems to be low... and less than boron. Is there any way we can work out exactly what ppms this is adding and perhaps clone it?

 

[Zeus.]

Is there any way we can work out exactly what ppms this is adding

Should be straight forward to get the ppms bit of maths from the percentage values on the label.

 

[Zeus.]

Will have a go at the maths when I get back from Lisbon. Was checking out the masters tank yesterday 😀

 

[dw1305]

Hi all,

Should be straight forward to get the ppms bit of maths from the percentage values on the label.

You need to find the volume of liquid dispensed by "twenty pumps", and then it is @Zeus.'s suggestion of a bit of maths involving the percentage of each element (in the <"Colombo Flora Grow Pro">) and the volume of the tank.

I dumped in 30 pumps of some Flora grow pro special fertiliser (colombo) in the tank this morning before lights on and looking now at midnight my rotala has sprouted out an inch from each node! Leaves are plumper too! There are new roots forming also which was always an issue with all plants.

My guess would be that that is a macronutrient effect and quite probably nitrogen. Looking at the analysis most of the nitrogen is in the form of ammonia (or urea), so that would become instantly available to the plants.

So - this is clearly a trace issue, at least for me and for whatever reason.

I think you can actually discount both zinc (Zn) and boron (B), purely because they aren't mobile within the plant, so there would be a lag period, longer than 12 hours, before changes in plant growth occurred.

Anecdotal bit
I don't have any fish at the moment in my kitchen tank, so I've been giving the tank an occasional "slosh" of urea rich <"Miracle Gro Soluble..."> fertiliser. I don't know exactly how much I've been adding, but it would still be a fairly small amount, and the result has been quite startling.

I thinned the floaters out about twelve days ago, some I sent to @NathanG, and others I put on the pond. The tank went from a complete covering to about 1/3 covered. It is now back to a fairly complete covering, mainly because of the growth of the Frogbit (Limnobium laevigatum). you don't really get a sense of scale from the photo, but the plants are really big and chunky. I took the photo on Thursday, this morning the central (five leaved) plant has six fully expanded leaves and is 20 cm across.



cheers Darrel

 

[HiNtZ]

Will have a go at the maths when I get back from Lisbon. Was checking out the masters tank yesterday 😀

It's 1 pump per 5 litres - 7 pumps = 10ml

Would appreciate the workings out if you can, no rush.

 

[HiNtZ]

Hi all,You need to find the volume of liquid dispensed by "twenty pumps", and then it is @Zeus.'s suggestion of a bit of maths involving the percentage of each element (in the <"Colombo Flora Grow Pro">) and the volume of the tank. My guess would be that that is a macronutrient effect and quite probably nitrogen. Looking at the analysis most of the nitrogen is in the form of ammonia (or urea), so that would become instantly available to the plants. I think you can actually discount both zinc (Zn) and boron (B), purely because they aren't mobile within the plant, so there would be a lag period, longer than 12 hours, before changes in plant growth occurred.

Anecdotal bit
I don't have any fish at the moment in my kitchen tank, so I've been giving the tank an occasional "slosh" of urea rich <"Miracle Gro Soluble..."> fertiliser. I don't know exactly how much I've been adding, but it would still be a fairly small amount, and the result has been quite startling.

I thinned the floaters out about twelve days ago, some I sent to @NathanG, and others I put on the pond. The tank went from a complete covering to about 1/3 covered. It is now back to a fairly complete covering, mainly because of the growth of the Frogbit (Limnobium laevigatum). you don't really get a sense of scale from the photo, but the plants are really big and chunky. I took the photo on Thursday, this morning the central (five leaved) plant has six fully expanded leaves and is 20 cm across.

View attachment 124560

cheers Darrel

I thought it might be macronutrient but have been dumping plenty in (also went super lean before that) - was even dosing urea and didn't see any changes while using the APF. Just a massive accumulation of N by the end of the week.

Could it be that the plant had reserves of the micros but something else was stopping them being used at the rate the plant wanted?

Your frogbit looks incredible - nice waxy healthy green leaves. Have you got a thread going at all?

I'm just waiting on the CSM+B to come Tue/Wed. I'll probably start a diary too.

 

[X3NiTH]

This is the dosage instructions as stated on their website.



So the dosage instruction is 1ml/5L. This product appears closely similar in composition to Seachem Flourish Comprehensive (not considering the chelates, just the levels) but in a different concentration (1/10th) and interestingly like Comprehensive it's got the exact same percentage of Cobalt in it at 4mg/L. Cobalt is not a listed ingredient in either the CSM+B or the APF traces.

 

[dw1305]

Hi all,

Could it be that the plant had reserves of the micros but something else was stopping them being used at the rate the plant wanted?

Certainly can be for some of the nutrients, it doesn't work for the non-mobile ones because they would just stay stock-piled where they were originally deposited.

It is really difficult to work out exactly what causes any specific deficiency, you've got 14 separate nutrients required for plant growth and then there are the possible interactions between them, the effects of pH etc.

Your frogbit looks incredible - nice waxy healthy green leaves. Have you got a thread going at all?

I haven't, I'll take some more pictures when I get time. I only took that one because I don't usually have really healthy Frogbit and if I need a picture I'm reliant on using @Timon Vogelaar's pictures from <"An Iwagumi....">.

I just chucked some more out onto the pond, and it really is a mutant ninja turtle fluorescent green.

cheers Darrel

 

[dw1305]

Hi all,

This product appears closely similar in composition to Seachem Flourish Comprehensive (not considering the chelates, just the levels) but in a different concentration (1/10th) and interestingly like Comprehensive it's got the exact same percentage of Cobalt in it at 4mg/L. Cobalt is not a listed ingredient in either the CSM+B or the APF traces.

Plants have a cobalt (Co) requirement, but I'm not sure any-one has quantified the minimum level before it becomes inhibitory to plant growth and it is going to be a very small number.

I don't know, but I'd be very surprised if the various sellers of aquarium fertiliser are making up their own trace element solutions from scratch. I'd expect that they are using <"commercial mixes">, probably ones designed for growing glasshouse tomatoes etc. in <"rock-wool">.

The actual cost of the fertiliser in a bottle of branded liquid fertiliser is going to be very low, almost all of the budget is going to go on the packaging, transport (you are moving a lot of water) and advertising.

Ready made, ready to use, fertilisers are convenient but are always going to be more expensive than using dry salts.

When we used to do more plant work in University, I used to make up separate micro-element solutions so I could create "minus boron" deficient etc. hydroponic mixes, but even using analytical grade reagents so of them "don't work", so the plants are getting enough of the missing micro-nutrient from somewhere.

Deficient macro-nutrient solutions work really well, and so do magnesium and iron from the meso-nutrients (as many of us have found out in our tanks .)

cheers Darrel

 

[X3NiTH]

Very small numbers indeed.

There is one way I see to end up with a possible Cobalt deficiency if it's not specifically being added as a nutrient and that it's not another contaminant of another element (base salt purity issue) and I think this could be the differences between water changes in using Tap Water or remineralised RO/DI, with tap water there is a very high likelihood of there being a low natural background concentration of Cobalt present but when de-mineralising the same water using RO/DI the overall concentration will be magnitudes reduced. If there is good biological filtration then a large colony of bacteria which can utilise Cobalt could deplete this much further, however this is transient though as it's eventually excreted back out as Cobalamine (Vitamin B12) which is a suspected nutrient source for BBA, so if plants are suffering and BBA has a hard time growing it may be lack of Cobalt.

Not saying this is the missing magic ingredient because too many things changed at once in the trace concentrations in the FloraGrow to pin a problem to one element, the total concentrations are lower than what's been dosed before but an extra element has been dosed where it was missing before and a positive change in growth behaviour was observed.

Trying to pin deficiencies on things measured in parts per billion/trillion is super hard!

 

[dw1305]

Hi all,

Not saying this is the missing magic ingredient

Cobalt chloride (CoCl2.nH2O) is the colour changing element in "Silica gel" (blue is anyhydrous, hexahydrate pink). You can ignore the silica gel bit and just grind up one or two blue (or pink) silica gel granules.

cheers Darrel