# Carbonate, bicarbonate and CO2



## timdz

*General plant inquiry confirmation*

With my minimal plant history knowledge... I have a question

In most planted tanks I've seen, we are combining plants from all over the world. I have been assuming that all plants will grow 'best' with maximum dissolved CO2 and supplement of macro / micro nutrients and trace elements.

Although I have read that most species of vallisneria and cryptocoryne extract their carbon from carbonates in the water, making them ideal for hardwater (high GH and KH) tanks.

Does this mean that they are able to tolerate the hard water or would they actually grow better in a higher pH / KH environment? To my knowledge, most val. comes from eastern asia, and am curious about recreating a natural environment.

I have seen some very beautiful val growing in pH of 6.8 and dKH of 4 with the inclusion of CO2 fertilization.

I am attempting to generalize here, and please correct me if I'm wrong... but
all aquatic plants require similar available nutrient levels. It's just that val, crypts, crinum thaianum, can tolerate lower levels of dissolved CO2 and extract the necessary carbon from the 'carbonate hardness'.

If I am trying to recreate a natural environment for certain plants, at this point, I would still try to have adequate lighting (2-3 wpg) with CO2 fertilization, even if I was trying to keep only 'hardwater' plants.

Bringing up 'carbonate hardness' brings up one more point. With most KH tests I've used it seems that they test for the water's ability to neutralize acids, but it still leaves the question of which carbonates or bi-carbonates are performing this action. Sodium bicarbonate and calcium carbonate in my opinion can have very different reactions on your system but can still supply an 'adequate' KH... therefore measuring your dKH with simple test kits is meausring the tanks proton sponge, and not very precise with actual carbonate hardness.

any info would be helpful
best regards,
Tim


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## Error

In Walstad's book, she shows an experiment she did putting Vallisneria sp. in two jars with soil, one containing soft water and the other hard. The one in the hard water grew much more than the one in soft.

I imagine that this kind of experiment is not necessarily precise, but I do have a hypothesis about why the plant in hard water did better. Suppose that Vallisneria uses both CO2 and bicarbonate, but prefers CO2. In an evironment with already low levels of available CO2 (as in these jars), the plants may have turned on their bicarbonate machinery, so to speak. Of course, only the one in hard water had access to far more bicarbonates, and thus grew more.

I think you will find that with good CO2 and fertilizers, Val will do just as well as it would in harder water. This seems to be the case for many hardwater plants.

Softwater plants, on the other hand, have IME been a different story.


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## timdz

So we can generalize that all aquatic (submerged) plants grow best with maximum available carbon and macronutrients?

I was answering a question for a friend who is more into saltwater biotopes and recreating those conditions. But for aquarium plants this doesn't seem necessary... Its only important that we provide what aquatic plants (in general need), and as long as they are provided proportionately, they will thrive.

Thanks for the info,
Tim


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## plantbrain

No,m all plants and algae for that matter prefer CO2, that's what ultimately used in fixing carbon and incorporating it into the Calvin cycle.

If you use CO2, then use it properly.
Add enough, you should not see a decline in the alkalinity(KH-> HCO3, the bicarbonate) unless the the CO2 is limiting for the given light level.

It is only under limiting conditions that algae, plants will use HCO3.
There are main two ways plants do this, indirect and direct bicarb use.

Diana Walstad does not add CO2. So given a situation where CO2 will become limiting.........having an ample supply of HCO3 will grow plants better than then same case without high KH.
about 50% or so of the aquatic plants are able to use bicarb and about all algae can.

Regards, 
Tom Barr

3rd annual Plant Fest July 8-14th 2005!
[email protected] Get connected
www.BarrReport.com Get the information


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## Error

timdz said:


> So we can generalize that all aquatic (submerged) plants grow best with maximum available carbon and macronutrients?


Well, that as well as light and micronutrients. As Mr. Barr noted, CO2 is generally preferred over bicarbonates, which are only utilized by the plants when there is insufficient CO2.


timdz said:


> I was answering a question for a friend who is more into saltwater biotopes and recreating those conditions. But for aquarium plants this doesn't seem necessary... Its only important that we provide what aquatic plants (in general need), and as long as they are provided proportionately, they will thrive.


Generally this is true. Some hobbyists have found, however, that certain plants seem to thrive when others do not, and this has led to the belief that there are plants that prefer softer water over hard. Tonina and Eriocaulon spp. are examples of plants that reputedly prefer softer water.

Aside from these, plants from all types of native environments can thrive together in the same aquarium. You do not need to replicate a given biotope to provide for the needs of a given local grouping of plants; they are as adaptable as fish are.

Another thing to think about when pondering this question is the concept of "good enough engineering" in terms of evolution and physiology. Though a given organism may be found in abundance in a certain environment, chances are that the organism in question has evolved _just enough_ to be able to survive and reproduce in that environment. In other words, there may be other environments in which it will do just as well or better--one cannot always assume that a plant's native environment is the environment in which it will display optimal growth.


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## Phil Edwards

Your plants will actually do better if given CO2 supplimentation. Carbon will be available in much higher amounts and in a free Carbonate form that is much easier for your plants to access than if a KH buffer were added to the water. Plants do have the mechanisms and physiology available to remove carbon from Bicarbonate, but it costs them energy to do so. 

Please see the Aqueous Carbon Chemistry thread I've posted for the nitty gritty details and chemical babble that's supposed to make it easier to understand.


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