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A long boring post on PH, CO2, Buffering, plus questions!

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A long boring post on PH, CO2, Buffering, plus questions!
Old 02-18-2010, 12:15 PM   #11
 
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You are playing games that are very dangerous with fish in the tank. You should never mess with CO2. I really can't understand what you are doing. As I pointed out in another thread,. that chart thing is not reliable nor accurate. It is also (I suspect) part of a larger process using CO2 supplementation.

If your tap water is pH 6, and you want to raise it for livebearers like guppies (and I agree it must be raised), a small amount of dolomite gravel will do so and keep it steady for years. I speak from experience. With tap water at pH 5 and zero hardness I maintained three large tanks at a constant non-fluctuating pH of 6.2 with about 4 tablespoons of dolomite in a nylon bag in the top of the canister filter on each tank. This lasted for years before I replaced the dolomite, and I'm not sure that it even needed it then. This also raises the hardness proportionally with the pH so the buffering is there and the tank is stable. In your case a small amount of dolomite would raise the hardness and pH slowly and you monitor it and add a bit more until you get the pH where you want it. The hardness is also essential for the livebearers, so you achieve everything simply and cheaply.

Byron.
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Old 02-18-2010, 12:19 PM   #12
 
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Originally Posted by redchigh View Post
I may not have been clear... right now I'm not supplementing CO2. I just calculated my CO2 using the chart.

I'm not sure, but I think maybe the chart doesn't tell you exactly how much CO2 you have, but rather the maximum amount that can be dissolved? I have no idea.

According to the chart though, lowering your KH would somehow magically add CO2 to your water.


Right now I do have an airstone attached to an air pump, and the PH is not swingling nearly as wildy as I thought. It did raise by .2 degrees in about an hour, but now, checking it the next day, it's 6.4. I think it's climbing slow enough to not harm the fish... Don't you think?


and yes, I have test strips. I get paid tomorrow, and I plan on buying the "Tetra Laborrett Water Test Kit".
The test will test for:
Freshwater PH
Carbonate and general hardness
Nitrite ammonia
is that good? If there anything else I need to test for?

The chart is used when you supplement CO2 and it's really only an estimate. You don't use that chart when you are not supplementing CO2.
It runs off the relationship of CO2 with KH and the affect on the pH. When you add CO2, you are adding a carbonic acid and, when the carbonate in your water reaches its limit of buffering, your pH goes down. From that relationship, it can calculate the estimated amount of CO2 you have.
The more carbonate hardness you have, the more it is buffered and your pH will be more steady. If you are not adding CO2, then you will not have more CO2 dissolved in the system by only increasing your KH.

To know how much CO2 exists in your tap water would take an entirely different test which I don't think the standard hobbyist can test for.

Here is a good explanation of the relationship:

Quote:
CO2 is added to water creating Carbonic Acid:
CO2(g) + H2O(l) --> H2CO3(aq)

Being an acid H2CO3 will dissociate and release a Proton(H+, a Hydrogen atom without the electron) into the solution forming Bicarbonate (HCO3-)
Here's the dissociation equation:

H2CO3(aq) --> HCO3-(aq) + H+(aq)

CaCO3 is added:
CaCO3(s) + H2O(l) --> Ca+2(aq) + CO3 2-(aq)

We now have in solution an acidic Proton (H+), Carbonic Acid (H2CO3), Calcium (Ca), and Carbonate (CO3 2-). These four substances will react to form and aqueous solution containing Hydronium Ions, Calcium ions, Calcium Bicarbonate, and Carbonate.

H2CO3(aq) + CaCO3(aq) -->/<-- H+(aq) +Ca 2+ (aq) + Ca(HCO3)2(aq) + CO3 2-(aq)

This actually results in the increase in the concentration of Carbonate in solution for a moment. In this system Carbonate is the conjugate base of Carbonic Acid. Those free acidic protons are quick to react with the free Carbonate to form Bicarbonate and Carbonic Acid again.

H+(aq) + CO3 2-(aq) --> HCO3-(aq)

or

2H+(aq) + CO3 2-(aq) --> H2CO3(aq)

Therefore, we have a buffered solution, which is why we use CO3 to buffer our pH. Keep in mind, this is nearly instanteous so there will be no change in KH measurable by our hobby test kits.

What we have here is a weak acid-weak base titration which will continue as long as we keep adding our acid. As we add more CO2 to our artificial environments the concentration of Carbonic Acid increases until the concentration of CO3 2- in solution (KH) is no longer able to compensate and the pH goes down.
So your KH is what will affect your pH. I've heard of people adding crushed coral to increase the KH but I've never tried it.
GH (general hardness) affects osmosis. If you plunk a fish into a solution with a different GH than what they had been in, it will affect their organs. But in general, changing the GH doesn't affect your pH like a change in KH.

You have to be very careful messing with the hardness of your water. When you have swings in pH and hardness, it's very stressful for the fish. It's much easier to make water softer than it is to make water harder.
I hope I helped.

Last edited by Claudia1002; 02-18-2010 at 12:30 PM..
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Old 02-19-2010, 04:26 PM   #13
 
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Question

I thought calcium carbonate would increase Kh...

(and BTW, my PH is 6.0 again. At least, assuming 6.0, it may be lower- the liquid's lowest scale is 6.)

I took the driftwood out, working on increasing Calcium Carbonate (which is chack, and the active ingrediant in dolomite gravel.)
Should I place the CaCo3 in a direct water flow(the filter or the airstone)?

I added dolomite gravel (about 1 tbsp) to my substrate weeks ago, and still- ph is 6 (or lower?!)

Any other ideas?
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Old 02-19-2010, 04:50 PM   #14
 
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Was this my tank I'd add 1 sp full in to a lil mesh bag that hand close to the filters outlet each day until the point I see it rise slowly and then add every 2nd day until such point its stable at the pH you wanna have it.
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Old 02-20-2010, 11:16 AM   #15
 
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Agree, or in the filter. The dolomite has to have water flowing through it and mixed in the substrate the effect will be less, though in time it would do it.

I suspect the chalk is too unreliable, it dissolves quickly but wears out, whereas dolomite is slow-acting for years. It takes a while for rock (which is what it is) to dissolve.
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Old 02-20-2010, 12:09 PM   #16
 
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Quote:
Originally Posted by Byron View Post
Agree, or in the filter. The dolomite has to have water flowing through it and mixed in the substrate the effect will be less, though in time it would do it.

I suspect the chalk is too unreliable, it dissolves quickly but wears out, whereas dolomite is slow-acting for years. It takes a while for rock (which is what it is) to dissolve.
Well I just thought lil bag so you can add slowly bit by bit each day or every 2nd day (thinking of my Eheim canister here I'd not wanna open it EVERY day lol)
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Old 02-20-2010, 02:23 PM   #17
 
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Originally Posted by Angel079 View Post
Well I just thought lil bag so you can add slowly bit by bit each day or every 2nd day (thinking of my Eheim canister here I'd not wanna open it EVERY day lol)
Yes, either will work. As it is a long-term solution, once the amount is resolved it can go in the filter out of sight.
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Old 02-20-2010, 03:35 PM   #18
 
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I guess I'll just have tp waot and see. (when I mentioned that I took out the DW, I think I forgot to say I did it a month ago, when I forgt noticed the PH)

I have two sticks of chalk right now laying above the airstone, so the bubbles hit them. (plus, so I'm reminded to check the PH every time I look in the tank. in the filter, I'd probably forget.)
So far, no noticable change, but I did an experiment to test the PH of chalk, (ground some into a powder, and dissolved about 1/4 tsp of chalk in 5ml of water) and the PH was 7.8.

Has anyone heard of calcium affecting plants in a negative way? just wondering because my apono looks... different... I think it might just be entering a different phase of growth though. (some seeds sprouted, and several leaves died, but now it has more leaves and a new flower spike. maybe I just need to prune the really old leaves off. they seem to be developing spots where the leaves are transparent. Could that be from the calcium, or the PH, or something?

Actually let me go test the PH again.

Okay, the PH is... drumroll please...
Well, it's hard to say what the number is, but it's an improvement.
(my PH color chart has yellow as 6.0, and it gradually gets greener until it gets to blue. blueish-green (more blue than green) is 7.5. The test showed my water as closer to 6 than 6.2, but there is the tiniest green tint that wasn't there before.
I guess I'll say it's 6.1.

YAY an improvement!
jeex its going to take a while :-/

on a bizarre note, I tested the water of my other ten gal tank. It's in another room, but the same setup and everything. I moved my driftwood into that tank. it's ph is reading 7.0
makes no sense.
(and its not those stupid ferts, I used them in two tanks. Also, the ferts are Basic, not acidic as the strips showed. The ferts have a ph of 8. (don't worry, I wont use them in my tank, was just investigating.)
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Old 02-20-2010, 04:35 PM   #19
 
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Spots with transparency are certainly related to nutrients, though it may be an excess of one or a deficiency of one or more. Calcium is a macronutrient required by plants and usually is in sufficient quantity in tap water to supply the plants' needs. Peter Hiscock writes, "In most cases, calcium should not be added artificially to the aquarium, as an excess will limit the availability of other nutrients and raise water hardness." Aponogeton occur in very soft acidic water. I've forgotten (if it has been mentioned) what the GH and KH of your tap water is, but unless it is near zero it will contain all the calcium the plants need, which is why you have to be careful how you add it for other purposes.
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Old 02-20-2010, 07:12 PM   #20
 
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So does that mean I have to choose to save either my plants or fishes?!

I guess I'll have to do a bunch of wc's and go buy some gravel :-/

oh and btw, I read somewhere that if there's not sufficient CO2 in the cater, plants can use carbonates for photosynthesis instead (with some effort). Just a useful little tid-bit.
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