newbie question: why is high ph and hardness bad for plants?

bluemeate

bluemeate

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Sep 9, 2008
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so whats the deal with the chemistry that makes it hard to growplants in high ph hard water?
 
even a link would be fine, i couldnt really find much
 
As the pH increases the inorganic carbon shifts from carbon dioxide (CO2) to bicarbonate to carbonate. At a pH above 8 there is essentially no carbon dioxide in the water. Plants need CO2 to grow and therefore since less and less CO2 exists as the pH increases your plants do worse. If you want some technical papers PM me with an email address and I will send you some pdfs.
 
i have giant vals in a brackish tank with 8.2ph and its at 15% seawater in salinity. So either not all the CO2 is converted to bicarbonate or brackish plants have a way to convert it back. If you have high ph tap water then any brackish tolerable plant should handle your water conditions.
 
thank you doc, that told me more than like the hour i spent on the web trying to figure out exactly wth was going on

does diy c02 injection work? or will it all be converted faster than the c02 can get to the plants? cuase the guy i got the plants from who lives by me told me to do that...

although he never said thats the reason why, he just said to do it.
 
carbon dioxe and water from to make carbonic acid, carbonic acid is a weak one but will still dissasociate into the water causeing hydronium ions to form (H30) which is the molecule that lowers ph.

CO2 will drop you ph, but only alot of it, will drop it alot. And i know once you increase it over a certain level its harmful to fish.

best way to safely drop ph, and the cheapest, is to add driftwood into the aquarium. This will drop your ph anywhere from .1-.4 over a few weeks. But also give the water a tea colored appearnce.
 
i have like 3 small pieces in a 55gal, should i get like 2 large pieces? Should i not even bother with diy co2?
 
Dropping your pH without CO2 will not help the plants, they will grow better without injection in HARDER KH's............actually.........

Since KH(more specifically HCO3) can be used as an alternative to CO2.

So if you want more plant growth, add CO2, do not add "acids".
Plants use CO2 to grow, or some will reluctantly take HCO3 if little CO2 is available.

So if you want more CO2, add more CO2:cool:

Sort of simple.
Stay away from pH and trying to out fox plants with that.


Regards,
Tom Barr
 
interesting, so can you explain why plants will do better without CO2 injection in a high carbonate hardness environment without me having to have a chemistry degree :P
 
jonny5 said:
interesting, so can you explain why plants will do better without CO2 injection in a high carbonate hardness environment without me having to have a chemistry degree :P
Click to expand...

Because the total available Carbon(sun total of both CO2 and HCO3) is higher than in soft water.

This assumes that the plant can/will use HCO3.
Some cannot. In this situation, plants that can do this, have a distinct advantage competitively over other plants.

So Vals, Hydrilla, Egeria, pondweeds, most all algae can. The "bad aquatic weeds" in general can do this very well. Rare nicer species, tend not too, but they can become weedy in theur make it to the surface where there is light and CO2.

All plants grow better/faster with CO2(Vals do about 10-24X faster for example). So.......add CO2 if you want to help.

Then perhaps more ferts, lastly.............consider more light.
Tropica has a good explanation for CO2 and light also.
http://www.tropica.com/advising/technical-articles/biology-of-aquatic-plants/co2-and-light.aspx

http://www.tropica.com/advising/technical-articles/biology-of-aquatic-plants/co2-table.aspx

The table shows that you can have optimal CO2 at any pH/KH............and to do this, we add CO2 gas.
This adjust the CO2 and the pH.

The pH is is a partial way to measure the CO2 via the KH.
But.....the real issue is still the CO2.






Regards,
Tom Barr
 
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