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Hi Everyone,

Well, I've been working on setting up my planted tank and it is coming along nicely. So far I have a 30L with Flourite substrate, a 96W compact flourescent light fixture with a 67K bulb, and NO CO2. We happen to have extremely hard water out of the tap, and I generally keep fish that are comfortable with this to avoid the expense and/or headache of changing the water.

I had not given this much other thought, but my husband went to an open house someone was having yesterday. The man had something like 40 planted tanks that looked amazing, and he has kept planted tanks for many years. They (my husband and him) got into a discussion about my tank, and our hard water. It was his opinion that I will never need CO2 because of our hard water because the hard water is in essence carbonate hardness which he explained was basically what CO2 attempts to accomplish.

I was astonished because I have never heard this before, but he had 40 planted tanks that were thriving and he did not use any CO2 at all. He had soft water and simply buffered the water to acheive the carbonate hardness.

So, anybody familiar with this concept already? What do you all think?

Thanks,

Tamara
 

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Discussion Starter · #3 ·
Ok, so maybe his explanation was lacking something, or something was lost in the translation, but what about the general idea that if you have hard water then CO2 is unnecessary? His tanks were obviously doing well without it?

Tamara
 

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Some plants can use the carbon that is in one of the compounds that make up KH to grow. Some others can't. Regardless, it's no substitute for CO2 injection. When the plants "eat" your KH it can cause your tank to become unstable and even lead to a toxic "crash" when the KH becomes so low it no longer buffers the pH to safe levels.

This type of growth is a more common way for ecosystems to support the plants we grow but largely impractical in aquaria. Most ecosystems have water supplys in the thousands if not millions of gallons of water so plants going for KH is no problem.
 

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Regardless, it's no substitute for CO2 injection. When the plants "eat" your KH it can cause your tank to become unstable and even lead to a toxic "crash" when the KH becomes so low it no longer buffers the pH to safe levels.
MemphisBob, welcome to the board!

Agreed, its no substitute for CO2. And he may and probably is doing lower light tanks, perhaps with NO regular T12 flourescents. Which is fine below 2.5 watts per gallon rule. But over that threshold one needs CO2 or algae will present an incredible problem.

Regards pH crash, well, IMO that has been fairly well debunked. There are some pretty interesting threads on that here and over at APC. One can have a CO2 overdose, or have a tank with almost too low of KH, but many now are keeping fish and plants that thrive at near zero KH. In fact some of the Eriocaulons and Toninas won't thrive at anything over 2 KH.
 

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Regards pH crash, well, IMO that has been fairly well debunked
Sorry Bob, I had not caught that yet. Just one of the bits of bad info this hobby is full of.

Back to the subject at hand, if KH crash is not a problem then it seems down to:
1. It can be done but plant selection will be affected.
2. Plant growth WILL change the KH of the water. Anyone know of problems this may lead to?
3. Plant growth will likely be somewhat slower using this technique.
4. Algae can easily become a problem in this setup.

This is more a Walstad approach so I'm not very familiar with it so maybe someone else can educate us both.
 

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In my experience it is somewhat the other way around... comparing tanks that are NOT supplied with CO2, I found it easier to grow plants in softer water.

With hard water, CO2 supplementation made a huge difference for plant growth.


I am not saying you shouldn't use CO2 with soft water, or can't grow plants without CO2 in hard water. Just sharing an observation opposite to what is mentioned in the OP.
 

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Sorry Bob, I had not caught that yet. Just one of the bits of bad info this hobby is full of.
Bob, nothing to be sorry about - its a very new theory... :smile: You are right, KH does buffer the water which I suppose is a given. . Yet as I mentioned, some folks have experimented with not increasing their KH (by using baking soda or crushed coral) to bring up their KH which is depleted over time with CO2 injection. And they have had no problems with soft water fish and shrimp apparently. Still, CO2 overdoses do happen, especially if one is near zero KH, which leaves the tank with little to no buffer. But if one is careful about the amount of gas, then there seems no problem, and the plants can truly flourish in a very low KH environment. That said, the current thinking is some GH (5 or so) is necessary. But some folks who grow amazing plants, like Craig (Wolfenexx) regularly uses straight RO/DI water on some of his tanks with near zero Kh and GH. Go figure.

But personally, I think I prefer a KH of 3 or so. This fairly new theory was started by Edward (I think?) over at APC. If anyone is interested there is a pretty interesting thread here too. And sorry since I got off topic. Here is the link
http://www.plantedtank.net/forums/g...no-kh-low-ph-without.html?highlight=Low+Crash
 
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