Low KH and pH crash - Page 6 - Fertilizing - Aquatic Plant Central

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Old 07-15-2006, 02:35 PM   #51 (permalink)
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As long as there are no fish or shrimp in the tank you can raise the CO2 amount as high as you want, just to see what effect it has, or to try to zero in on the bubble rate that gives maximum benefits. Since you have to wait to add fish, why not use the time to experiment? It won't harm the plants.
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Old 07-15-2006, 10:38 PM   #52 (permalink)
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Quote:
Originally Posted by hoppycalif
As long as there are no fish or shrimp in the tank you can raise the CO2 amount as high as you want, just to see what effect it has, or to try to zero in on the bubble rate that gives maximum benefits. Since you have to wait to add fish, why not use the time to experiment? It won't harm the plants.
Thank you Hoppy. My current bubble rate is 3bps and I did see bubbles forming behind the java fern and bolbitus, but I have cranked it up now, I can't tell how many as it is pretty fast, let's see what happens. Next week I will be adding shrimps and Ottos, so till then I can play around with it. I do however switch off the CO2 at night, should I leave it on 24/7? BTW the KH is still below 1ppm.
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Old 07-16-2006, 08:36 AM   #53 (permalink)
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Originally Posted by Skyfish
Thank you Hoppy. My current bubble rate is 3bps and I did see bubbles forming behind the java fern and bolbitus, but I have cranked it up now, I can't tell how many as it is pretty fast, let's see what happens. Next week I will be adding shrimps and Ottos, so till then I can play around with it. I do however switch off the CO2 at night, should I leave it on 24/7? BTW the KH is still below 1ppm.
If you don't have any fish or shrimp it doesn't make any difference whether or not you shut off the CO2 at night, other than the CO2 usage, and the time to reach maximum CO2 in the water each morning. I think the goal of this exercise is to teach you what the tank looks like when you are absolutely sure you have plenty of CO2 in it. That makes it much easier to recognize when you don't.
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Old 07-16-2006, 09:30 AM   #54 (permalink)
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Originally Posted by guaiac_boy
First of all, in a planted tank, who cares about nitrifying bacteria? The plants take up so much that most of us have to add it back in.
With billions of such bacteria, I think this is another blow the assumption that C02/carbonic acid/pH is an isolated, independent system behind the pH change dissolved CO2 chart. Secondary changes will be going on at least in the background because a large biosystem has been throttled back by a pH change. We could really use an inexpensive way to directly measure the dissolved C02 to know what is going on.

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I think Edward's approach of keeping fish in a KH of zero is interesting, and reveals that a lot of what we pass around as "fact" probably isn't.
Humans recognise patterns, whether valid or not. Perhaps I could become rich starting up an aquatic plant religion where people started noticing good things happen when they send me donations to construct a temple to a yet-to-be-defined diety.

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An understanding of the principles behind the physiology and chemistry is more important than trying to get parameter "X" to a certain value.
But that's not how most people "learn". It's easier to have a religious faith based upon pH crash killing fish, when it could be something else (i.e. pH was actually lower, but it was an effect not the cause of the fish deaths.) They saw dead fish, lower pH, therefore confirmation!

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Regarding the KH/CO2/pH chart...... It works perfectly well as long as carbonic acid from CO2 is the only acid in the system and carbonates are the only buffers. Since this is never true, the chart can never be expected to be accurate.
This is conceptally nasty because hardnes and the resulting equilibrium states between a buffer and the dissolved ion/acids of the mineral plus the interaction between free H and free OH and is conceptually quite difficult.
Quote:
Decomposition of fish food, fish waste, plant matter, driftwood, and other compounds will inevitably introduce organic acids that accumulate with time.
And other stuff in the aquarium which dissolves much more readily when pH drops. You can and probably do have significantly more dissolved "crud" in the water if you drop the pH from 6.5 to 5.5. That could also be a factor in the 'pH crash' fish deaths.

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I suspect that most of what gets reported around the internet as a "pH crash" is actually an ammonia spike. A low plant mass with an overstocked tank and a poorly functioning biofilter is a perfect setup. Nothing kills fish more quickly. A sudden increase in CO2 is also pretty impressive. I've seen this kill fish in a matter of minutes.
That might be. By the time one gets to measuring this with test kits, the ammonia spike may have gone away since the system can handle a certain base rate which will absorb temporay spikes. People notice the next day they have dead fish, but their ammonia and nitrates test out at zero.

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Being vertebrates, the biochemistry that takes place in a fish is pretty similar to our own. Hemoglobin is the carrier of oxygen in the blood stream and it looses its ability to carry oxygen when CO2 levels get too high.
Because hemoglobin can't dump CO2 into the air when the air is already nearly saturated with CO2. The same thing can happen to fish. In this way, too much CO2 can directly kill fish via a fairly simple to understand mechanism.

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When humans experience a gradual increase in CO2 (such as in lung disease), blood pH goes down and our kidneys compensate by producing more bicarbonate and dumping more acid.
Don't think the kidneys can produce bicarbonate. Other functions in the body will dissolve bone if neccesary to keep pH from getting too low.

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I think Edward is right that high CO2 levels can be more toxic than low pH levels. For most people though, it's hard to understand the difference. This is probalby due to the fact that we're all accustomed to equating pH to CO2.
Because most people don't have a science background, so they stuck memorizing religious type rules such delta pH change equals dissolved CO2. The biggest problem is that people don't understand that this is an estimator with a +/- error range since this is never included in the charts to make them easier to understand. How can one calibrate this? Without such calibration, we don't understand the margin of approximation (i.e. error) in what we read off the chart.

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Still, there is a certain pH below which the fish can't adapt. This exact point differs between species.
Even this is a nasty experiment. In your tank you could have something that dissolves in the water only at a very low pH and that is what really killed the fish, even though you can only measure that the fish started dieing off at pH 5.3. You would need a bare tank with just fish and multiple acids in different tanks to see if a common low pH killed the fish.[/quote]

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Whew, what a novel....... sorry
One needs a novel to resolve each sub question!

Last edited by ruki; 07-16-2006 at 09:36 AM..
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Old 07-16-2006, 12:27 PM   #55 (permalink)
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Wow ruki, quite a lenghty response. One of the primary reasons that I enjoy planted tanks is that there is ample subject material for thought. It's nice to stretch one's brain once in a while. It's probably pretty obvious to most people on this board that I sometimes stretch mine a bit too far, hehe.

I am wondering about what you mean by this statement though:

Quote:
Originally Posted by ruki
Don't think the kidneys can produce bicarbonate. Other functions in the body will dissolve bone if neccesary to keep pH from getting too low.
Maintainence of blood bicarbonate is a primary function of the kidney/gill. It might be more correct to state that they regulate readsorption vs excretion, but for all practical purposes it results in the same thing - more bicarbonate in the blood.

As far as I know, skeletal catabolism isn't a primary mechanism for pH control. Osteoclasts will increase their adsorption of bone as a result of many stimuli, but most often this is in response to serum calcium levels, phosphate levels, or various endocrine disorders.

Sorry to get so far off-topic. Your point about other potentially toxic substances dissolving more readily at low pH levels is a good one. In at least one area though, low pH levels can be protective. Ammonia toxicity will be almost impossible at a pH as low as Edward is talking about since it will virtually all be converted immediately to ammonium.
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Old 07-17-2006, 02:35 PM   #56 (permalink)
 
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To respond to my message about problems caused by low PH on Nitrifying bacteria.

Coming from US Environment Protection Agency

A very interesting paper (PDF 15 pages) on Nitrification

http://www.epa.gov/safewater/tcr/pdf/nitrification.pdf

I quote:
Quote:
nitrifying bacteria are very sensitive to pH as shown in Figure 3. Nitrosomonas has an optimal pH between approximately 7.0 and 8.0, and the optimum pH range for Nitrobacter is approximately 7.5 to 8.0. Some utilities have reported that an increase in pH (to greater than 9)
and 2 other interessant point on the consomation of bicarbonates in amonia-nitrogen oxidation and the final effect of low KH on PH stability.
I quote:
Quote:
A model developed by Gujer and Jenkins (1974) indicates that 8.64 mg/L of bicarbonate (HCO3-) will be utilized for each mg/L of ammonia-nitrogen oxidized. Reductions in alkalinity can cause reductions in buffering capacity, which can impact pH stability.
I donít know if all the paper on the subject of lower KH that destabilize PH are baloney but they are very clear to me.


Even with all the nice theory out there, putting your hand in fire will always burn.
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Old 07-17-2006, 07:31 PM   #57 (permalink)
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Glouglou,

Yes, exactly! As ammonia is taken through the nitrogen cycle, acid is produced. It's basic proton chemistry. If you start with NH3 and end up with NO3- those protons went somewhere. To greatly simplify, they end up in solution as acid and this "consumes" some of the available bicarbonate. What you see is a pH drop. This makes up part of the "organic acid" that I refer to when stating that the pH/CO2/KH chart doesn't work very well.
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Old 07-18-2006, 07:04 PM   #58 (permalink)
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Quote:
Originally Posted by guaiac_boy

I am wondering about what you mean by this statement though:

Quote:
Originally Posted by ruki
Don't think the kidneys can produce bicarbonate. Other functions in the body will dissolve bone if neccesary to keep pH from getting too low.
Maintainence of blood bicarbonate is a primary function of the kidney/gill. It might be more correct to state that they regulate readsorption vs excretion, but for all practical purposes it results in the same thing - more bicarbonate in the blood.
I was taking the absolutist position that the kidneys regulate pH by choosing to dump or not dump something. They don't produce it, it's initially absorbed by the intestines. They get it from the blood and choose to release it or not. They can store it in intermediate forms to supply buffering capacity, but there is a limit to how much can be stored in the buffer.

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As far as I know, skeletal catabolism isn't a primary mechanism for pH control. Osteoclasts will increase their adsorption of bone as a result of many stimuli, but most often this is in response to serum calcium levels, phosphate levels, or various endocrine disorders.
I'm not a medical person, but may have read too many articles which sometimes are oversimplifed to the point of being misleading. One of the frequently repeated health tips for osteoporosis is to not drink carbonated beverages since this will try to raise the pH of the body. If you do not consume enough high pH items, the body will dissolve bone to maintain equilibrium. The kidneys can not produce enough bicarbonate if you don't consume enough base materials and instead consume lots of carbonated beverages. Is this accurate or inaccurate?
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Old 07-18-2006, 07:50 PM   #59 (permalink)
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Boy, we're really off-topic here. I think I might pull this whole section out and start a new thread in the waterbucket to clean up the original thread.

The issue with carbonated beverages is that most of them contain huge quantities of phosphates in the form of phosphoric acid. Calcium regulation in the body is closely tied to serum phosphate levels. When phosphate levels are high (such as in renal failure or excessive soda pop consumption), the body tries to get rid of calcium. Uptake of calcium from the intestine is also slowed down.

To see clinical long-term effects such as osteoporosis you'd need to drink colossal quantities of soda over a period of many years, but that certainly doesn't exclude many people here in the US.

With regards to bicarbonate, it's a pretty simple molecule and the body has many enzymatic mechanisms for producing it and breaking it down in various locations. It isn't transported across the lumen of the glomerulus or the lumen of the gut in its native form. The actual transport occurs as CO2. A little acid-base aqueous chemistry, mediated by enzymes, and presto......., for all intents and purposes, HCO3- is produced. The enzyme carbonic anhydrase (also present in plants, allowing them to extract carbon directly from carbonate) is involved in this process.
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Old 07-26-2006, 04:58 PM   #60 (permalink)
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I once spoke with a co-worker who had a kidney stone. He refused to give up the soda though. So, the dumping of Calcium gets done via the kidneys and has little to nothing to do with the carbonate used to balance body pH?
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