_Maq_
Member
If pH drops on degassing, it's not the proof of what you are saying - that the tap water would be naturally much higher in dissolved CO2. It would be a proof of the opposite.
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Lean dosing pros and cons
- Thread starter Riverside Scaper
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Ah sorry yes, typo on my part, a pH increase on degassing. My post corrected.
_Maq_
Member
sparkyweasel
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- 30 Jun 2011
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Which is why we sometimes get 'pearling' on hardscape, glass walls, filters etc.
I have some time ago - I’m an RO user not tap so haven’t measured recently, but digging out the pH meter to run a test just now for the purposes of this conversation:
Water fresh from the tap:
Water from the same tap that’s been standing for a good 12 hours+:
Taken with a calibrated Hanna Halo HI11102.
Alkalinity at this time of year approximately KH7 give or take.
Someone smarter than me can probably estimate the difference in dissolved CO2 that could be accounting for the difference in pH, but the overriding point being at an approximate pH0.7 difference it’s not an insignificant amount of additional dissolved CO2.
_Maq_
Member
Some 28 ppm decreased to 5 ppm. But it strongly depends on alkalinity.
Still, it's a strong argument that you're right - and I was wrong - in that a fresh tap water can contain remarkable amount of CO2. Wow!
Indeed it does and that's a fact. Tap water can contains a good amount of CO2 due to how the water is processed in water plants before it is sent back into the pipes. This is not intentional but a consequence of the water treatment processes.
GreggZ
Member
Agreed. Tap water can contain a good deal of CO2. The same for well water. I've got well water going through an RO system, and even after the RO the water still contains CO2.
Many people make the mistake of testing pH right out the tap. It's always best to fully degas and age it for a few days. And it can cut both ways.
Sometimes there is CO2 added which lowers pH, and there can also be other things (like sodium hydroxide) added that raise pH. Either way best to let a sample to come to equilibrium with atmosphere before testing.
I'm back a little late but the conversation still seems relevant.
Thank you I was not aware of this possibility. I did have in mind the possibility of adding CO2 via tap water.
To know if the CO2 contribution comes from the new water or from the atmosphere, I think a test could be done with a false water change: empty the tank and fill it with the same water from the tank. If the plants grow well / better with this false water change, this would indicate that the capture of CO2 from the air is effective for their growth.
Thank you I was not aware of this possibility. I did have in mind the possibility of adding CO2 via tap water.
To know if the CO2 contribution comes from the new water or from the atmosphere, I think a test could be done with a false water change: empty the tank and fill it with the same water from the tank. If the plants grow well / better with this false water change, this would indicate that the capture of CO2 from the air is effective for their growth.
With the pictures I think your tanks are better. Have you ever tried to stop changing the water in your tanks? With the lean dosing it seems that it could work but there is still the question of CO2 input with these water changes.
G
Guest
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That’d be one way of doing it. If you leave tap water to degas in a container overnight it’d be pretty safe to assume CO2 levels would equilibrate with atmospheric levels.
Although I have not done this with any of my non-CO2 supplemented softwater tanks but I have been experimenting with Ammannia pedicillata golden in a small plastic container. It has been almost 4 months since I have done any water change and I also added huge amount of ammonia containing root tab but the plants are still doing okay (top leaves are getting smaller since I posted the last update on June 20.)
We can't directly correlate this with actual planted tank but I still think it is somewhat informative.
Here is the link;
sudiorca's non-CO2 supplemented softwater tank
www.plantedtank.net
_Maq_
Member
I disagree. Marschner's numbers are valid universally. Only monocots require much less Ca.
However, plants differ significantly in their abilities to uptake nutrients upon differing external conditions, par example pH.
Mostly, not exclusively. But yes, uptake of other forms is of minor significance, perhaps with the exception of P.
To that I'd add that toxic levels are difficult to detect. I suspect toxicity of micronutrients happens more often than we believe.
I suggest that a community called UKAPS should adopt strictly negative attitude toward commercial blends of nutrients, aka "universal" fertilizers. Nothing of that sort can ever exist. It may be a way for beginners or less engaged hobbyists, but a forum dedicated to aquatic plants should be aware of its inherent limitations.
In natural habitats, P and N (less often) are usually limiting nutrients. Plants are adapted to that. My experience strongly suggests that if these two are in short supply, plants grow slowly but signs of nutritional imbalance seldom appear. On the other hand, if N or P are plentiful and any other nutrient is not in adequate supply, plants show signs of nutrient deficiencies.
So I suggest we stick to N & P when talking about "rich" or "lean". To me, lean dosing is close to what plants know from their natural habitats. I define it not by its content in water column (P is difficult to measure, and most of it is in the substrate, anyway; ammonium also tends to get adsorbed to organic matter in the substrate) but by the content in the water I use for water change.
Usually, I change 20 per cent water weekly, and that water contains 1 to 3 µM P (0.1 to 0.3 mg/L H3PO4) and 16 to 48 µM N (equivalent to 1 to 3 mg/L NO3). The actual amount available to plants is supposedly lower because of plant and microbial consumption. In any case, it is still more than in most natural habitats. Keeping these levels, my plants do not stunt and rarely show nutrient deficiencies, but they grow relatively slowly.
Can we call it "lean dosing"?
Although soft and acidic waters are typically low-nutrient in the nature, I don't see good enough reasons for tying lean conditions exclusively with them. Like I said, it's the content (or, more precisely, availability) of N & P which defines "lean" and "rich".
I'm hesitant when reading words "nutrient-rich substrate". A very clean silica sand is relatively "passive" substrate, meaning its sorption ability is low. However, once it gets enriched with decaying organic matter (detritus), adsorption increases significantly. From then on, individual nutrients behave in their own natural ways. Nitrates, chlorides, sulfates, molybdates do not adsorb, so they do not accumulate in the substrate. Ammonium, sodium, potassium, magnesium, calcium, and boron adsorb on clays, if present, in differing degree (subject to the type of clay and ambient factors like pH), and partially on detritus. Phosphorus and transition metals tend to desert water column rapidly both because of microbial uptake and adsorption.
I've experimented with enriching substrate with purified clays, zeolites, ferric oxide, charcoal, and peat. None of them is a source of nutrients per se, they just enhance adsorption of selected nutrients. In theory, keeping nutrients within the substrate should be a good anti-algae measure, and some reports confirm that it may work in natural waters. My experiments did not lead to any remarkable results, so the question remains open to me.
Enriching sediment with fertilizers in pills/tabs? Many aquarists report good results. It depends. If they release nutrients too quickly, microbes (not plants) will be the first to gain advantage and proliferate. With that, some negative development may occur. I don't use them.
Neither do I! Plants should be stressed from high concentrations of nutrients. Microbes should flood the tank. Phytoplanton should quickly dominate and suppress macrophytes by light attenuation. Yet it does not happen. Why?
My only suggestion (pretty weak) is that plants massively supported by CO2 produce in excess secondary metabolites incl. those which may have an allelopathic effect.
Excess K is not a problem in relation to N & P, but in relation to Mg, Ca (and Na). The latter happens pretty often, it's perhaps the most widespread source of nutritional defects.
Micros cannot be effectively measured. Yes, I follow Marschner when preparing my stock solutions; it's a good measure not to overdose. But then, I follow what the plants tell me. Iron deficiency occurs most often by far. Those who use tap water should know that tap water very often contains more than enough micronutrients. Again, with the exception of iron.
Marschner is a good starting point, yet it cannot be followed in practice. Firstly, plants uptake some nutrients preferentially in relation to others. Typically, K vs. Mg & Ca, or P vs. S. Secondly, in many cases the question of availability is decisive. So it's not bad to dose Fe and Mn in 2:1 ratio, but in the end, you have to observe your plants and detect the signs of deficiency.
I would never suggest dosing micronutrients on regular basis, without plants' feedback, and most of all, I find outright dangerous to use commercial blends of micronutrients. They are made for farmers. Conditions in fields differ substantially from those in our tanks. The main difference is that in the field many micros are lost due to leaching, but in a tank, transition metals accumulate! Typically, Tenso Coctail is rich in molybdenum, because Mo (unlike other transition metals) poorly binds to soil particles, and much is lost due leaching. Another difference is that in fields, oxic conditions prevail. The presence of oxygen is decisive in making micros (and phosphorus) soluble or insoluble.
_Maq_
Member
In spring, I tested Ammannia crassicaulis and Ludwigia glandulosa. In broad terms, tanks A and B (from left to right) were acidic, tanks C and D were alkaline. Tanks A & C featured lean dosing (16 µM N), tanks B & D rich dosing (160 µM N).
You can see that both plants were able to utilize increased doses of N & P. Thus, they don't belong among the group of slow-growers. (Slow-growers are generally unable to benefit from increased available nutrients, so, in nature, they are outcompeted in fertile biotopes. On the other hand, they invest in durability of their tissues, so they can "wait", while "fast-growers" cannot cope with nutrient-limited conditions. Roughly speaking - for details, ask @Simon Cole).😆
Secondly, you can see that Ludwigias stunted in C & D. All tanks were freshly established and in all of them, I took pain to dose all micronutrients in the very same amount. Ammanias prospered both in acidic and alkaline conditions, but Ludwigias were unable to uptake micros in alkaline water. So, increased dosing of micros was of no use if the given species cannot manage. (More detailed pics and mineral composition of water can be submitted if anyone interested.)
You can see that both plants were able to utilize increased doses of N & P. Thus, they don't belong among the group of slow-growers. (Slow-growers are generally unable to benefit from increased available nutrients, so, in nature, they are outcompeted in fertile biotopes. On the other hand, they invest in durability of their tissues, so they can "wait", while "fast-growers" cannot cope with nutrient-limited conditions. Roughly speaking - for details, ask @Simon Cole).😆
Secondly, you can see that Ludwigias stunted in C & D. All tanks were freshly established and in all of them, I took pain to dose all micronutrients in the very same amount. Ammanias prospered both in acidic and alkaline conditions, but Ludwigias were unable to uptake micros in alkaline water. So, increased dosing of micros was of no use if the given species cannot manage. (More detailed pics and mineral composition of water can be submitted if anyone interested.)
Thats an interesting photo, thanks for sharing. 2 observations:
While C & D appear to have slower growth, the red colour of the Ludwigia glandulosa in C& D appears to be more attractive.
Ammannia crassicaulis didn't turn red under lean dosing and remained very green
While C & D appear to have slower growth, the red colour of the Ludwigia glandulosa in C& D appears to be more attractive.
Ammannia crassicaulis didn't turn red under lean dosing and remained very green
_Maq_
Member
It looks nice but it's due to lack of chlorophyll. So it's a defect.
Most likely, my plants were genuine Ammannia crassicaulis. Most A. c. in the trade are actually Ammannia gracilis which takes orange-reddish hue much more easily. In my experience, A. crassicaulis remains yellow even under intense light. But yes, under high-tech high-light high-all treatment things may turn differently.
Hi all,
This is the Third Edition of <"Marschner’s Mineral Nutrition of Higher Plants">. Personally <"I'm not after optimal growth"> etc., I just want some plant growth.
There are inherent limitations of <"commercial fertiliser mixes">, but there is also the disclaimer that commercial hydroponic fertilisers must fulfill the basic requirement of promoting plant growth, or they companies that make them would have gone out of business.
I'm going to stick by what I wrote earlier in the thread, and I'm going to carry on recommending <"Solufeed 2 : 1 : 4"> etc.
You may well be right.
This is the Third Edition of <"Marschner’s Mineral Nutrition of Higher Plants">. Personally <"I'm not after optimal growth"> etc., I just want some plant growth.
I can see where you are coming from, and many of our members do use dry salts, but I think it is a <"bit of a stretch"> to expect people to buy all the individual salts to make up their own <"micro-nutrient mixes"> etc. and I'd guess that even the people who do make their own mixes are going to use a commercial <"trace element mix">.
There are inherent limitations of <"commercial fertiliser mixes">, but there is also the disclaimer that commercial hydroponic fertilisers must fulfill the basic requirement of promoting plant growth, or they companies that make them would have gone out of business.
I'm going to stick by what I wrote earlier in the thread, and I'm going to carry on recommending <"Solufeed 2 : 1 : 4"> etc.
cheers Darrel
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GreggZ
Member
While I find the results interesting in a very general broad sense, IMO it does not really “prove” much at all.
The problem with these types of experiments is that it doesn’t account for the many other variables from tank to tank. Pretty much what this proves is what happened in those particular tanks, with that particular set up, and those particular plants.
Let’s say we add CO2, or vary the concentration of CO2, how do plants react? Let’s say we provide a fresh nutrient rich substrate, what happens? Increase light? Decrease light? Increase water changes? Decrease water changes. Add fish? Increase dGH? Decrease dGH? Change dGH Ca/Mg ratio? Vacuum substrate regularly, never vacuum substrate? Add more micros? Add less micros? Vary macro nutrient composition and ratios? More PO4, less PO4? Add more K? Less K?
And I could go on and on.
In the real world with a real tank all these variables are at play every day. Each tank is a unique ecosystem. And not to be lost is that different plants have different optimal conditions. You may set up a tank to grow something like Rotala Wallachii perfectly, but when you add 20 other species you will realize that they may have different preferences.
What I find far more interesting is someone who can keep a wide variety of plants at near peak health and create something beautiful. And I do understand that is not your focus. But even so the plants in these tanks do not look to be in peak health. Lot’s of algae on old growth and the substrate looks dirty with algae as well.
I think sometimes folks make the mistake of looking at a tank like a science experiment. In my experience it’s part science and part art. Heck even something as underdiscussed as pruning/horticulture skills can make the difference between success and failure. A technique that works with one plant might cause another to fail. The only way to learn these things is with time and experience.
Heck I have planted the same plant in three different spots in my tank and two flourish and one fails? All seemingly in the same conditions. Just saying the mysteries of the planted tank are not easily solved like a math problem. And of all the things that make for a great planted tank, nutrient dosing is probably the least important. A well run planted tank can get by well on a wide range of nutrients and a nutrient centric approach many times leads to failure. People can’t see the forest through the trees.
Funny thing is that when you get to know some of the best in the hobby not once does the discussion of Marschner's ratio come up. In fact dosing is pretty low on the list of what is discussed.
Hi all,
cheers Darrel
I'm pretty sure that is right.
That is also basically where I'm coming from. I've been using "lean dosing" with a ~90% silica sand substrate with a small addition of Oak (Quercus) or Beech (Fagus) leaf mold and neutral clay <"for a long time now">.
Agreed, I don't think there is any point in trying to measure micro-nutrient levels in the tank, I'm also much keener on "watching the plants", and it is a <"scientifically valid"> method. It doesn't work <"particularly well for iron (Fe)">, which is, as you say, a <"common, and easy to recognise, micro-nutrient deficiency">.
Agreed as well, it is the <"horses for courses"> argument. I've framed it in terms that you wouldn't try and grow <"Orchids and Tomatoes"> in exactly the same growing conditions, so why <"should all aquarium plants be the same">?
Same for me, a <"shades of grey world">. Personally I'm <"reasonably good with plants">, but <"I'm still cr*p with fish">. I've got better, but <"from a very low starting point">.
Same for me again.
cheers Darrel
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I do not have a chemistry/plant biology background, so I am happy to keep it simple.
For someone like myself, it seems to make sense to buy a bottle of ferts off the shelf and dose the tank with it. At roughly 1 ml a day, my 500ml bottle will last me more than 1 year.
Hi all,
Personally I'm much too mean to give my money to the participants in the <"World's most expensive water"> competition, but I'm also much too lazy to actually make up my own fertiliser any more, when there is a <"cheap, and acceptable, compromise"*>.
* I realise that it won't be an acceptable compromise for every-one.
cheers Darrel
I guess that is it, if people can buy an easy to use, off the shelf solution that works they will, and why not?
Personally I'm much too mean to give my money to the participants in the <"World's most expensive water"> competition, but I'm also much too lazy to actually make up my own fertiliser any more, when there is a <"cheap, and acceptable, compromise"*>.
* I realise that it won't be an acceptable compromise for every-one.
cheers Darrel
