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What causes leaves to melt, and what to do now?

jalexst

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Having planted a 14l nano, the following day all leaves on the Ambulia Conferta and Micranthemum Micranthemoides had melted. There is a little melting on the Saurogyne but the other plants are fine (HC and Eleoacharis)

I am doing 50% water changes daily in the Initial stages and dose easycarbo 0.25mil and tpn+ 0.17mil daily. The tank is now 6 days old.

So how come everything melted so quick and what do I do now? I have left the plants as they are for now.

Thanks for your expertise! :thumbup:

Jack
 

ceg4048

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Hello,
Melting is caused by insufficient CO2 for the given lighting level. Add more Excel or reduce the light intensity, or add more flow, or any combination of these.

Cheers,
 

jalexst

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Thanks Ceg,

I am sure the flow is fine, So I will up the easycarbo and see what happens...

In the meantime, what about the melted plants? do I just need to give them time to recover or will they not recover?

the Micranthemoides has melted right down to substrate level...

Cheers,

J.
 

ceg4048

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Hi,
I really cannot say. Melting is dying, so it depends on how much has melted. If the roots have not melted, and if there is a little bit of stem left then the plant might have a chance to recover - assuming that the CO2 has improved sufficiently. Sometimes, the leaves melt but the plant is able to adjust to the CO2 level so it puts out new growth and is fine afterwards, without any change in the CO2. It all depends on the plant as well as how much light, flow and CO2 are available and whether these values cause enough damage to kill the plant, or whether the plant is able to make the adjustments quickly enough to save itself. I've seen large scale meltdown followed by complete recovery as well as permanent meltdowns...

Cheers,
 

jalexst

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Ok, I guess I will have a little patience and see what happens. Thanks Ceg,

Also does the length of the photoperiod make a difference? Having had great success in my other tank on 5 hours of light, I have started this one off the same...

Cheers mate, great help.
 

ceg4048

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Hi mate,
The photoperiod has an effect, but it is always within the context of the effects of intensity. So for example suppose the plant is not receiving enough light to produce food. No amount of photoperiod can compensate for that. On the other side of the coin, if the intensity is too much then the damage to the plant is being done by this intensity and a longer photoperiod means that the damage is being done for a longer time. Shortening the photoperiod reduces the total amount of damage, but the damage is still being incurred.

When the intensity is higher than the minimum required, but lower than destructive levels, then the photoperiod will regulate the total amount of food production.

Hope this makes sense...

Cheers,
 

jalexst

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OK, took a couple of reads but I got it...

I understand what you mean regarding the photoperiod and intesity of light, but have just a couple of questions...

Firstly what do you mean by "food Production?" is this relating to the production of Oxygen, and therefore growth?

also, slightly further off topic, when using the manufacturers recomended dosage on things like easycarbo and fertilisers, should the length of the photoperiod be taken into consideration? since surely the longer it is, the more nutrients are used up by the plants, right?

Thanks for all your help Ceg, I am always fascinated by your posts,

J.
 

ceg4048

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Good stuff mate,
Food production is an expression that not many people associate with aquatic plants, yet if I said we were talking about a potato plant or an apple tree it would be a little easier to grasp right? The whole point of plants using light is to produce food. That food is the end product of photosynthesis. The Carbon that is in Carbon Dioxide (CO2) is combined with Nitrogen, Phosphorous and other nutrients to make a carbohydrate - sugar.

Sugar is the end product of photosynthesis. The plant then eats the sugar and that is what fuels growth. So when you think about what a plant does during the photoperiod you should always think about sugar production first, because this is the key. If a plant suffers a "nutrient deficiency" the result is a reduction in sugar production, which equates to loss of food and results in malnutrition.


Again, few people think about the fact that plants eat sugar and breathe oxygen to burn that sugar in order to produce the energy required for growth. This is exactly the same as for us or for animals. Have you ever forgotten that you had a potato in a cupboard somewhere, and discovered it months later? What does it look like? Most likely it has turned into a plant, and what was the potato has shriveled in nothing more than skin. The plant ate the potato and used the carbohydrate energy to grow leaves and roots in order to start the cycle all over again. And grew in complete darkness, but once the potato is consumed, there needs to be more food and the job of chlorophyll is to use light energy to produce food, so in the dark the plant begins to shrivel because it cannot produce carbohydrates without the light energy.

A more technical explanation.

Fruit trees and nut trees are particularly talented in making sugar, so much so that there is a surplus of sugar, and this is what we pick from the tree to eat. When we eat the carbohydrates in the fruit, our cells burn the sugar using Oxygen and the carbon from that very same sugar is recycled as waste and is expelled from our lungs as CO2. So Carbon and Oxygen are caught in an infinite loop where they are taken from air, by plants, algae and some bacteria, hydrated with water turned into sugar, burned for energy and expelled as CO2. It's a miracle.

Light is used to power the reactions of sugar production. When you plug in you light bulb and shine it at the plant the light that reaches the plant leaves is, in a way, "plugging in" the plant, because light and electricity are actually two sides of the same coin. Light produces electricity and electricity produces light. But what happens if you add too much electricity to a bulb for example? The filaments in the bulb can only handle so much electron flow. Adding too much burns out the bulb, and so it is with plants that they can only handle so much electron flow. So if you add too much light, then the areas of the plant that handle the electricity created by the light also burn out and this stops sugar production. If sugar production stops it's only a matter of time before the plant uses up it's reserves of sugar and after that it starves to death.

When you think of light therefore, you must think in terms of electricity which "plugs in" the plant and allows it to power the chemical reactions used to make sugar:

Therefore, we have to regulate how much electricity is used to energize the plant, by regulating the amount of light being pumped into the leaves. If we don't pump enough light then the plant cannot generate enough electricity and it starves. If we pump too much light then the plant "circuits" burn out and it starves. The good news though is that if we can provide enough nutrients and CO2 then it makes these food production "circuits" more robust so that the plant can use the high light levels. Add more flow/CO2 and nutrients give the plant a much higher capacity to absorb and use the energy of the light.

So any time you see leaves falling off, or melting, or translucent, or stems rotting, or holes in leaves - any structural fault in the plant, then this tells you immediately that there is too much light/electricity for the plant to handle and that it is starving. That is fundamentally the root cause. How you fix the problem is up to you:
1. You can reduce the electricity.
2. You can increase the CO2 to bolster the electricity handling circuits.
3. You can make the plant more efficient at breathing the amount of CO2 that is there by improving flow and distribution.

As far as photoperiod relationship to dosage, it's not really something that you can easily adjust for. Primarily because plants can uptake nutrients even when there is no light. Nutrient uptake mechanism is a completely different beast than the way in which those very same nutrients are used.

Also, photosynthesis/food production itself has a time limit and is self regulated by the plant. This can only happen for about 8-10 hours a day maximum. Furthermore, when you dose a liquid carbon product, you are interested in increasing the concentration and therefore the availability of CO2, so there is no point in lowering the dosage just because you will only have the lights on for 5 hours because if you do that then you will have less CO2 for those 5 hours than you would have if you had dosed the proper amount. In fact, the situation is usually just the opposite. You often need to add more than what they suggest, because they assume that everything else in your tank is perfect, which is almost never the case.

As a result, you would be better off NOT trying to make dosage adjustments based on photoperiod because that would be like opening a can of snakes. :crazy:

Cheers,
 

spyder

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Clive.

Have you thought about a basic guide to light/co2/nutrient demands and their relation to each other? I know you cover it almost daily at times. The information is already out there but scattered about in chunks. To have it all in one post would certainly help newcomers.

One more thing, thanks for the education :thumbup: . Without your post's I'm sure my tank would not be flourishing as well as it is right now.

Cheers.
 

ceg4048

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Hi spyder-man,
Thrilled to know that you find the info useful mate. Yeah, I wanted to either rework one of the existing tutorials or submit a new one, but I always get stuck trying to determine how deep to go. Should it just be a primer level for the uninitiated, or should it be more comprehensive? To get a grip one has to touch on so many different areas but we'll give it a try since it has to be basic enough to not scare away the novice but yet have enough substance to not be fluff. Somehow it's easier when answering a question because I can usually tell from the question itself what concepts the user needs help in grasping, so that helps me to focus a response. I suppose I could collect some posts and stitch them together. I might try that and add a bit here and there, see what it looks like.

You're right mate, I wish I had just 10p for every time I had to address this subject. Somewhere in The Matrix there must be either a subroutine, or bot that programs Klingon worship within the humans of this sector of the Galaxy....

Cheers,
 

spyder

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ceg4048 said:
Hi spyder-man,
Thrilled to know that you find the info useful mate. Yeah, I wanted to either rework one of the existing tutorials or submit a new one, but I always get stuck trying to determine how deep to go. Should it just be a primer level for the uninitiated, or should it be more comprehensive? To get a grip one has to touch on so many different areas but we'll give it a try since it has to be basic enough to not scare away the novice but yet have enough substance to not be fluff. Somehow it's easier when answering a question because I can usually tell from the question itself what concepts the user needs help in grasping, so that helps me to focus a response.

May I suggest a 2 parter. Part I to cover the basics and importance of balance and the consequences of not getting it right.

Part II can go deeper. I remember so many little bits of posts but forget the whole picture from time to time. One thing that springs to mind was rubisco? Never heard of the word before but I can;t tell you what it is or what it does now without going to look it up again. Something to do with energy transport? :oops:

Anyway, yes I find it very useful having a better idea what's going on inside our aquariums.
 

ceg4048

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:clap: That's actually a pretty darn good question mate. That's kind of like asking why the sun shines, which seems like a child's question at first glance, until you realize that children have been asking that question for centuries and neither their parents nor anyone else knew the answer to it until the early 20th Century. It took Albert Einstein to figure it out, and even when he explained it, the explanation was so bizarre and far fetched that it blew everyone away. Strangely enough, when he explained the concepts to children they accepted and understood them. The adults with PhDs were left dumbfounded... o_O

And so, the answer to why you can't just add sugar is complicated, and it has to do with the way in which sugar is produced, the type of sugar that is produced, and the location in the plant where sugar is burned and where energy is extracted from that burning.

Every individual cell in the plant has to get it's share of sugar which is produced internally by the special chloroplast cells and then distributed to all the other cells by a network of "blood vessels" called the "Phloem" (pronounced flow-em). The sugar enters the cell via a specific pathway from the chloroplast and flows throughout the plant being grabbed as needed by individual cells. The sugar then enters the cell to an area called the "Cytoplasm" where preliminary breakdown of the sugar occurs, and which produces a product called "Pyruvate".

Here is a really cool website. On this page there is a little animation of sugar transport in terrestrial plants, which won't be exactly the same as in aquatics, but gives a general idea:
http://highered.mcgraw-hill.com/sites/9 ... ading.html

Inside each cell there is a miniature living battery called the "Mitochondrion". It is the function of all Mitochondria to combine Pyruvate with Oxygen to produce energy for the cell. This is how each Mitochondrion pays his rent, so to speak.

As far as I'm aware, sugar dissolved in water does not have an uptake mechanism in the plant. The plant normally leeches sugar from inside to out, which feeds the bacteria in the sediment. In fact, that's one of the symbiotic relationships plants have with bacteria. Adding sugar would therefore feed the bacteria in the same way as peat or detritus does, but there is no way I know of to get the external sugar into this network and of getting it distributed to the cells. Too much dissolved carbohydrates in the water column are really a source of pollution and actually block uptake of nutrients and CO2, so this is not really a good idea generally.

Cheers,
 

jalexst

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Nice one ceg :D , had to have a bit of a sit down to get my head around all this!

So a couple of things...

Photosynthesis/food production happens when the lights are on right? so, since we all know that CO2 is released by the plant at lights out, does this mean that the sugar consumption and growth is happening in the dark?

also, if nutrient uptake is happening around the clock, does this mean we can dose nutrients at lights on or lights off, and it have the same outcome so long as it is the same time each day? Sometimes I worry that I need to dose nutrients before the lights come on as if I miss it by an hour or so, that hour of the photoperiod seems wasted almost... since there wasn't any nutrients in the water at the time. if that makes sense...

Also regarding the liquid carbon doseage. If I have the lights on for a 5 hour period, I understand that I need the same concentration of CO2 in the water than if the photoperiod was longer. However, something in my mind is telling me that surely the plants "use up" the CO2 (liquid product) as the photoperiod goes on, therefore reducing the concentration, so how come the dose remains the same? :crazy: For example, when gas is used the Concentration remains the same throughout the photoperiod (exept for at the end) However, If the photoperiod was lengthened obviously the length of time the gas is released is longer, meaning... more gas. Though the concentration is still the same throughout. So, in that respect, how does it work when adding a liquid product all in one go, for an unspecified photoperiod? if that makes sense too... don't get me wrong and please don't open the can of snakes, just can't get my head around the difference.

One last thing :rolleyes:

When adding things to the water such as liquid carbon, and fertilisers, I (try my best to) add according to manufacturers guidlines and what I can see in the tank too. For example the melting that I have experienced. But. Without ever knowing how much is in the water and how much the plants are using, something else in my mind says "what about the excess?" because if I am doseing daily, and and there is a little excess daily, then does it build up and up until... something bad happens?

Cheers ceg, hope you don't mind all my questions, I really find all of this fascinating stuff :thumbup:

J.
 

ceg4048

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Hi jalexst,
No, I don't mind the questions at all. This is why we are here. 8)

jalexst said:
Photosynthesis/food production happens when the lights are on right? so, since we all know that CO2 is released by the plant at lights out, does this mean that the sugar consumption and growth is happening in the dark?
Well, consumption happens all the time. Every cell in your body as well as in the plants body has a job to do, and they need energy to do it, so there is a consant requirement for food. Our bodies build up food reserves in the form of fat and that fat is stored in many different locations for ease of transportation. So when we are not eating, the fat is converted back to sugar and feeds the cells. This is almost exactly the same in plants, except instead of storing food as fat, plants convert the sugar to starch, because starch has a much longer and stable shelf life than sugar.

Back to the potato, here is a view from an electron microsope inside a potato tuber, showing the stored grains of starch. Aquatic plants will do something very similar:
9271298582_12e3f088c1_z.jpg

Photo Courtesy of Dennis Kunkel Microscopy.

So the plants build up a starch reserve and can feed from this reserve. During the photoperiod the sugar that is produced replenishes the stored reserves. When the plant is under duress, such as with high lighting, the starch reserves get used up and the food being produced gets consumed immediately. If that is insufficient the plant might start to canabalize itself to feed the remaining portions and will jettison the parts that cost more energy to retrieve than it produces. CO2 is produced 100% of the time by all cells, but this CO2 is not retrieved. Oxygen is being consumed 100% of the time, yet Oxygen is also being produced by the plant. The thing to remember is that only certain cells in the plant produce Oxygen and only certain cells produce food. The vast majority of cells in the plant are strictly consumers of energy, consumers of Oxygen and producers of CO2. It's just that during the photoperiod the balance of Oxygen is a positive output, and the balance of CO2 is a positive input, sort of like profit and gain. The cells that produce Oxygen are producing more Oxygen than the amount of Oxygen being consumed by the other cells combined. The amount of CO2 being absorbed by the CO2 specialist cells is higher than the amount of CO2 being released by respiration of all the other cells combined. So it's not that plants only breath Oxygen and release CO2 at night, it's that the net consumption and production of these gases is different during day because the food machine operates during daytime and changes the balance.

jalexst said:
...also, if nutrient uptake is happening around the clock, does this mean we can dose nutrients at lights on or lights off, and it have the same outcome so long as it is the same time each day? Sometimes I worry that I need to dose nutrients before the lights come on as if I miss it by an hour or so, that hour of the photoperiod seems wasted almost... since there wasn't any nutrients in the water at the time. if that makes sense...
Yes, it makes sense. I understand what you mean, but this is something that you should never really worry about. The idea of dosing nutrients in the water column and in the sediment is to build up a concentration of nutrition that the plant has access to all the time. AS long as the concentration available to them is higher than the rate at which they pull the nutrients from the water/sediment then this becomes a non-issue. If you see signs of nutrient deficiency then this telss you that you are not dosing enough nutrients, not that you are dosing at the wrong time. Always do you dosing whenever it is most convenient for YOU.

jalexst said:
..Also regarding the liquid carbon doseage. If I have the lights on for a 5 hour period, I understand that I need the same concentration of CO2 in the water than if the photoperiod was longer. However, something in my mind is telling me that surely the plants "use up" the CO2 (liquid product) as the photoperiod goes on, therefore reducing the concentration, so how come the dose remains the same?
Liquid Carbon products are nowhere as effective as gas injection. First of all they have to be converted to CO2 within the plant, and any conversion or chemical reaction in the plant normally costs energy. Secondly, the liquid has what is described as a "half life" wherein after a certain amount of time, the concentration is half of what it was when initially dosed. Liquid carbon products are therefore best used as a supplement to gas injection instead of as a primary Carbon source, but it is still much better than not having any CO2 enrichment at all. One could dose twice during the photoperiod to keep the concentration levels up. Again, it depends on how much you want to amplify the growth rates. The good news is that carbon enrichment is much more important at the beginning of the photoperiod than it is nearer the tail end. People who suffer CO2 related problems can often solves these problems by ensuring a very high CO2 at the moment that lights go on and it will not matter that much if the CO2 is poor near the end. In fact my CO2 is shut down 5 hours into a 8-9 hour photoperiod. What's most important is that plants have a very poor eficiency at food production when the day starts, so I keep the lighting very low and the CO2 very high in the early stages to help them get started. Once the engine is "up to speed" so to speak, then they become very efficient and the concentration levels can sag without penalty, so again, this is not something to really worry about as they can make good use of the residual levels, even if the concentration is lower.

jalexst said:
..When adding things to the water such as liquid carbon, and fertilisers, I (try my best to) add according to manufacturers guidlines and what I can see in the tank too. For example the melting that I have experienced. But. Without ever knowing how much is in the water and how much the plants are using, something else in my mind says "what about the excess?" because if I am doseing daily, and and there is a little excess daily, then does it build up and up until... something bad happens?
Umm...I NEVER pay attention to manufacturers dosing recommendation. That's because manufacturers don't have my tank, with my lighting, with my flow, with my environmental stresses. So they have no clue about what's happening in my tank. In fact, I don't bother with manufacturer's dosing products at all if I can help it, because their nutrient products are about 100 times weaker than they should be.

Bad things can only happen when you don't have enough nutrition. As I explained in all my analogies, you must consider these products to be food. So the only thing that happens when you have excess food is that the plants gain excess weight, which is a lot better scenario than the one you have now, right? So in fact if you have double, trebled or even quadrupled the dosing that the manufactures recommended, we might not even be having this conversation now, because your plants may have been in better health. Having said that though, one has to be careful about liquid carbon products because they are toxic in much higher concentrations.

For a more effective dosing concepts review the thread viewtopic.php?f=34&t=1211

Cheers,
 

Viv

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I've enjoyed reading your posts ceg, you expalin things very well. But can I clarify something? You seem to be implying that photosynthes is a process that only occurs in light. But during the lighting period the plant only produces energy (stored as ATP). Its during the unlit/dark hours that it uses ATP to form sugars. Also, in the stepped cycle that produces sugars other carbon compounds are produced and subsequently used. I thought liquid carbon contained these carbon compounds and that the plant 'slots' these into relevant part of the cycle during the dark reactions?

Sorry if I've misunderstood what you've been saying, or haven't realised if you were just simplyfying things, but I wanted to check :)

Viv
 

ceg4048

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Hi Viv,
While there are some plants, like cactus or pineapple, that carry on with some segments of photosynthesis at night, the vast majority do not have have these capabilities. These special plants use a system called Crassulacean acid metabolism (CAM) where they collect CO2 at night and store the CO2 as a special acid called Malate. The stored Malate can then be broken down and converted back to CO2 to be used during the day when ATP and Ferrodoxin (NADP) can be produced by the light. Why use CAM? Well, the plants that use CAM mostly live in areas where water is scarce, so if they open up their pores to let in CO2 then water escapes, so the strategy is to keep their pores closed during the most arid conditions and to open the pores at night, when it's cooler.

Are there aquatic plants using CAM? Yes, absolutely, and the reason is similar, in some waters CO2 might be at it's highest concentration at a time of the day when the sun is not shining, possibly due to lower temperatures for example, so they collect CO2 and store it as Malate, then they wait until the sun shines to perform the entire sequence. Different plants will have different CAM abilities. Some may be better able to capture and recycle the CO2 released by respiration.

Generally, it is not really true that "only" ATP is produced during the day and is stored for night use. I'm pretty sure that this is a misinterpretation of the two main photosynthetic systems.

Photosystem 2, Also Known As PSII, is referred to as the light dependent System. This system is a series of protein complexes each of which performs a vital function. PSII is the system that uses the majority of the light energy to produce ATP.

On the other hand Photosystem 1 is referred to as the light independent or, dark reaction, and so many people think that this only happens in the dark, but this is not true. In fact it was discovered that PS1 needs light to produce enough energy to reduce Ferrodoxin. PS1 is where sugar is produced by a process known as The Calvin Cycle, and it uses the ATP that was just produced by PS2. So, the chloroplast does not store ATP because these molecules are immediately sent to the PS1 Dark Reaction center. PS1 and PS2 must work in concert, and they must do so in the light. The word "dark" was completely misused in describing this function. Even the expression "Light Independent" is a misnomer, because as I mentioned, PS1 has a protein complex known as P700, 700 referring to the maximum wavelength used by pigment cells in this protein to complete the Redox reactions necessary to complete the Calvin Cycle.

The other carbon compounds that you mention would all strictly be intermediates of, or subsequent conversion of the primary sugar 3GP (Glyceraldehyde 3-Phosphate). So for example an intermediate carbohydrate would be 1,3Biphosphoglycerate (3-PGA) and a subsequent conversion would be fructose or glucose (but these are post C-Cycle products). The 3-PGA is kind of a "pay the rent" carbohydrate for the cells doing this work.
Of course, since this is a cycle, there is regeneration, so some of the 3GP returns to the top of the cycle as RuBP, facilitated by the addition of a little more ATP.

I really have very little idea how Gluteraldehyde is handled metabolically, but Barr equates it to CO2, so whether this is actually CO2 that enters the Calvin Cycle or whether he is referring to it as CO2 schematically is unclear.

Cheers,
 

jalexst

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Wow :wideyed:

Thanks ceg this stuff is great... So I have now removed the melted plants, they had entirely melted even below the substrate. Since then I upped the liquid carbon dose and fertilisers and have been watching the remaining plants carefully. All is well today (couple of weeks later) so I have planted some new ones.

Just a quick one... You said that liquid carbon overdosed is toxic (same as CO2 I assume) Is that for fish and other inhabitants only or does an overdose have a negative affect on the plants. I only have plants in the tank at the mo while I am tweaking the doseage.

Also regarding the new article that was mentioned earlier... can you recomend any good reading on all this stuff? It's nice to be able to benefit from advice from somebody like yourself, but everything that I read (fish books and plant books) all seem to have the same stuff inside. And they all seem a bit dated (just read in a thread about a week ago that the mid photoperiod siesta to prevent algae growth was a myth!?)

Thanks again Ceg, I look forward to the article! :thumbup:

Jack
 

ceg4048

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jalexst said:
... You said that liquid carbon overdosed is toxic (same as CO2 I assume) Is that for fish and other inhabitants only or does an overdose have a negative affect on the plants...
Well, liquid carbon toxicity has nothing to do with CO2 toxicity. This needs to be very clear in our minds. The liquid is absorbed by the plant and is then converted by chemical reactions internal to the plant. The chemical agent of all liquid carbon products is a chemical called GLUTARALDEHYDE which is an extremely bio-toxic substance. Do a search on this forum for glutaraldehyde and you read some very alarming facts. These are some of the industrial uses of glutaraldehyde:
Most often used to disinfect equipment that cannot be heat sterilized such as dialysis and surgical instruments.
A tanning agent.
A biocide in metalworking fluids and in oil and gas pipelines.
An antimicrobial in water-treatment systems.
A slimicide (kills organisms in wood pulp that produce slimy excretions) in paper manufacturing.
A preservative in cosmetics.
A tissue fixative in pathology labs.
A hardening agent in the development of X-rays.
Used in embalming solutions.

Not all plants respond well at all to glutaraldehyde. In fact, more "primitive" plants such as liverworts and bladderworts are at it's mercy and will completely melt if the concentration is too high. Each plant seems to have it's own level of toxicity concentration. The mechanism is a cytotoxic attack to the tissues, meaning that the individual cell walls are disrupted and breached, spilling the fluid contents of the cell. That's how it kills bacteria and therefore sterilizes. So it does the same thing to some plant cells and some algae cells, and can do the same to shrimp in high enough concentrations. You should definitely keep it away from kids, avoid inhaling it and avoid getting it on your skin, just to be on the safe side.

It may also be that too high of a concentration level of gluteraldehyde disables one or more stages of the Light dependent reactions or of the Calvin Cycle reactions causing the same effect as if there was a CO2 shortage.

Of course the percentage of glutaraldehyde in liquid carbon is very low so the health risks are mnimized, but you should still be careful. The toxicity of CO2 is a completely different mechanism, and that occurs only in fauna, not in flora. Have a look at the information contained in http://ukaps.org/forum/viewtopic.php?f=21&t=14774

jalexst said:
can you recomend any good reading on all this stuff?
It's always worth checking out Diana Walstad's Ecology of the Planted Aquarium

jalexst said:
...(just read in a thread about a week ago that the mid photoperiod siesta to prevent algae growth was a myth!?)...
Yes, an unfortunate myth started by a famous aquatic supplier's marketing department. People who use siestas get just as much algae as anyone else, if not more. There are lots of myths, and they're not all debunked in the same place, so one just has to keep reading in the right places. You should also read the Newsletters on The Barr Report - but you have to pay to access the Newsletters.

Cheers,
 
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