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GH and KH observations, self adjusting?

This is a discussion on GH and KH observations, self adjusting? within the Beginner Planted Aquarium forums, part of the Beginner Freshwater Aquarium category; --> Originally Posted by TitanTDH Yeah mate, pretty happy with the water. Matches the plants and fish I intend to use. Just looking at upping ...

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GH and KH observations, self adjusting?
Old 01-24-2013, 06:15 PM   #11
 
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Yeah mate, pretty happy with the water. Matches the plants and fish I intend to use. Just looking at upping the gh and kh by 2-3 points to allow for plant usage. But I'll discuss that when the background is finished
That won't help plants any more. I aim for 5 dGH. And assuming soft water fish, the lower the GH the better.
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Old 01-30-2013, 06:21 PM   #12
 
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Today being water change day, I tested the GH to complete the experiment. To recap, last week the 50% water change halved the GH in all tanks and adding the Equilibrium resulted in an increase of 2 dGH in all tanks. Prior to today's water change, I tested GH and found in all tanks it is identical to the number last week after the water change. In other words, it is not lowering at all due to the plants assimilation of calcium and magnesium.

Of course, this is with the API test kit which is not high-tech science, but I think the results are probably close enough.

So, even with all my plants, they do not pull sufficient hard mineral from the water such that the GH will lower from week to week.

Interesting results.

Byron.
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Old 01-30-2013, 06:44 PM   #13
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Hmmm, then what I s going on in my tank I wonder... I'm going to test tonight or tomorrow out of curiosity. On the 26th it was at. 21dGH and 16dKH.

Jeff.
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Old 01-31-2013, 10:42 AM   #14
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Hmmm, then what I s going on in my tank I wonder... I'm going to test tonight or tomorrow out of curiosity. On the 26th it was at. 21dGH and 16dKH.

Jeff.
21st post 75% WC = 21dGH and 16dKH
22nd post 30% WC = 19dGH and 17dKH
25th no WC = 21dGH and 16dKH
26th added 9 catfish, 4 red hygrophila stems , 1/2 a tank surface of duckweed
31st no WC = 21dGH and 16dKH

Difference in the tank since the 26th would be an increase in ammonia concentration, measurable as "non-zero" so not near 0.25ppm except once.

Not a scientific result due to the non-static conditions but interesting that the hardness has not changed since the addition of the new ammonia source. I thought that the 25th result might have been false as I did not do the test myself, my daughter did, perhaps she miss counted as I wouldn't expect the GH to go up while the KH went down. Today's test confirms that the 25th test may have been correct.

Don't think I am going to get anything to explain it so I'll just chalk it up to just one more equilibrium to watch even though I don't know what the other side is.

Oh, here are some pics of the plant growth over the period.

1 = 20th
2 = 28th
3 = 30th

Seems to be a growth spurt in the last few days since the fish have been added.

Jeff.
Attached Images
File Type: jpg progress jan 20, 2013.jpg (71.4 KB, 13 views)
File Type: jpg progress jan 28, 2013.jpg (80.1 KB, 13 views)
File Type: jpg Progress Jan 30, 2013.jpg (76.6 KB, 14 views)

Last edited by JDM; 01-31-2013 at 10:44 AM.. Reason: added pics
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Old 02-05-2013, 07:56 PM   #15
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I did a little more thinking and research on this and realized what may have been going on and why it changed when I added the second batch of fish.

I thought it was the plants using the CaCO3 for the calcium, which it could very well have been but reducing the KH by as much as 25% or more in such a short period seemed a little much... how much calcium can plants take up or more to the point, how much calcium can plants need.... but what do I know?

Seeing as the plants are growing very well, I didn't really need to look too closely at what was really going on. When I added new fish and the plants took off I figured that it was just the added ammonia production, could have been, it certainly was a factor but certainly not the only one.

What I failed to realize is that plants take up a LOT of Carbon... seeing as plants are something like 45% carbon by dry weight it makes sense that they need a lot, and the rate that my plants are growing, they would need far more carbon than calcium.

Initially, with fewer fish (12 barbs), the CO2 generation in the tank was low, relatively. The plants needed carbon so they used the carbon from the low levels of CO2 produced by the fish and the high levels of CaCO3 in the water and reduced the carbonic hardness accordingly. I expect that CO2 is easier for them to use the carbon from so they would probably use it more readily... that is just a guess.

Now, with roughly twice the fish bioload (9 more larger fish) there will be about twice as much CO2 being produced by the fish, of course this is along with the higher ammonia production which helps to balance the system. I have noted that since the 9 additional fish the KH is not lowering as much... barely measurable in fact.

This leads me to believe my guess that the CO2 is used quicker than the CaCO3 and that it was, indeed, my plants directly reducing the KH in the water. Now that there is much more CO2 production, they are just using it first, or faster than CaCO3.

Of course I know that CO2 is often injected into systems to increase plant growth, I knew why but didn't really put it together with my KH adjusting system until now.

Jeff.
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Old 02-06-2013, 10:30 AM   #16
 
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That seems logical. Walstad cites some studies on the sources of carbon for aquarium plants. I can't go into all the scientific data in her chapter on this, but there is a list of plants that are effective at using bicarbonates as a source of carbon, and there is a list of those that cannot. Not surprisingly, the users of bicarbonates are many of the stem plants (the fast growers) and of course Vallisneria which is a hard water plant. Those that cannot use bicarbonates are the Echinodorus, Ceratopteris, lily-type, Ludwigia, mosses, to name a few.

Byron.
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