Help regulating pH, KH, & GH

[Cardinals]

Here's another way to look at the pH/KH relationship:
GH is a measure of primarily Calcium and Magnesuim which is unrelated to pH or KH in themselves.
KH is more correctly called 'total alkalinity' and is independant of GH.
KH is easily increased with the addition of bicarbonate based alkalis including sodium bicarbonate (baking soda ) and Seachem's "alkaline buffer" (sodium/potassium +/- other undisclosed bicarbonates, not calcium or magnesium).
There is a fixed relationship between total alkalinity and pH and CO2.
CO2 in the air is around 390ppm (and rising!). CO2 in freshwater aquaria is fairly constant generally only ~0.5 -3ppm. Good water turnover with pumps and aerators will reduce CO2 to the lower end of this range as the gas is released into the atmosphere at the air/water interface (surface).
For the planted aquarium, without supplemental CO2 or phosphate buffers, as KH (total alkalinity) rises, pH rises. As an example in a typical planted aquarium with a CO2 ~ 2 ppm:
pH 7.2 = dKH 1.0
pH 7.4 = dKH 2.0
pH 7.6 = dKH 2.5
pH 7.8 = dKH 4.0
pH 8.0 = dKH 6.0
pH 8.2 = dKH 10.0
pH 8.4 = dKH 25.0
As predicted, this is generally consistent with your observations. (tapwater pH 7.1, dKH1 ).
If you wanted a pH of 7.8, add sodium bicarbonate (i.e. unadulterated baking soda) or Seachem's alkali buffer daily at recommended doses until you have a KH of 3.0. Your pH will be ~7.8.
pH/KH/CO2 tables are readily available on the internet, have a look at the "CO2 table" at tropica.com or http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm.
You can not have a tank with a pH of 7.0 and dKH 6.0 without supplemental CO2.
However, you can add small doses of bicarbonate to neutralise some of the acids continually being produced in your aquarium and keep the pH above 7.0. You will not have much KH at this pH. The system is still stable in practical terms though.

A note regarding the use of the word buffering:
It can be seen that at dKH 10, pH 8.2 it requires a large increase (+15.0dKH) or decrease (-4.0 dKH) in alkalinity to change pH by only 0.2 units. This is where a bicarbonate based buffering system is most powerful in a planted tank. As can also be seen, the system does not have much buffering capacity at pH ~ 7.8 or less.

[Tech Support LK]

Thanks for the reiteration of the information JS supplied back in March :)

[QUOTE=Cardinals;6937] CO2 in freshwater aquaria is fairly constant generally only ~0.5 -3ppm.[/QUOTE]

Can you please reference where you got this information? I have been having difficulty finding factual info on the average amount of CO2 dissolved in FW. Any help would be appreciated.

[QUOTE=Cardinals;6937] the planted aquarium, without supplemental CO2 or phosphate buffers, as KH (total alkalinity) rises, pH rises. As an example in a typical planted aquarium with a CO2 ~ 2 ppm:
pH 7.2 = dKH 1.0
pH 7.4 = dKH 2.0
pH 7.6 = dKH 2.5
pH 7.8 = dKH 3.0
pH 8.0 = dKH 6.0
pH 8.2 = dKH 10.0
pH 8.4 = dKH 25.0
As predicted, this is generally consistent with your observations. (tapwater pH 7.1, dKH1 ).
If you wanted a pH of 7.8, add sodium bicarbonate (i.e. unadulterated baking soda) or Seachem's alkali buffer daily at recommended doses until you have a KH of 3.0. Your pH will be ~7.8.
[/QUOTE]


Why are your using 2ppm of CO2 as an average number when the very reference you linked us to says that typical level in planted aquarium is 3-4ppm? Also, based on your chart references I think your calculations are a little off in the above table you created. If I plug in 2ppm CO2 and 3.0dKH, I come up with a pH of about 7.653. Am I missing something?
Thanks!

[Cardinals]

Dear LK
You could do the same chart with CO2 4ppm, it is not the point. The point is that with a fixed CO2 (in equillibrium) KH and pH are positively correlated. As KH rises, so does pH, until pH approaches pKa (my guess ~8.2), and true bicarbonate buffering comes into effect.
Perhaps it would be worthwhile going through the thread again with an open mind? My post was not a reiteration. Some questions to highlight the issues about Seachem referring to these products as "buffers" for acidic pHs:
1) This customer was targeting pH 6.8-7.0, why did her pH rise from 6.2 to 7.5 on addtion of Seachems "buffers"?.
2) If the customer follows Tech Support JS's recommendations for a dKH ~2, what will the pH be?
2) What "buffer" is in the water at pH 6.5?
3) If you had a tank with pH 6.5 KH 0ppm, no supplemental CO2, no other buffers, and you added 1 dose Seachem acid buffer and 1.3 doses Seachem Alkaline Buffer, what would be your pH? What would be your KH? Why?
4) Another way is, for a given CO2, how can you raise the alkalinity with a bicarbonate, but keep the pH at 6.5?
5) Is the product at pH 6.5 a buffer or a pH up/down product? Why?

Does anyone at Seachem have a tank with pH 6.5 and "buffered" with Seachems buffers? If so, what is their KH?

Thank you pointing out the chart error which I have changed to KH 4.0. at pH 7.8.

[Tech Support LK]

Thanks for the questions. I have tried to answer them to the best of my ability below:

1) This customer was targeting pH 6.8-7.0, why did her pH rise from 6.2 to 7.5 on addtion of Seachems "buffers"?.

Customer was using baking soda when this occurred. Not Acid and Alkaline Buffer.

2) If the customer follows Tech Support JS's recommendations for a dKH ~2, what will the pH be?

Well now, that will be dependent upon many variables, such as CO2 concentration and most importantly organic acid load and production.

2) What "buffer" is in the water at pH 6.5?

At a pH of 6.5, assuming a bicarbonate-based buffer, there will be an almost equal mixture of bicarbonate and carbonic acid.

3) If you had a tank with pH 6.5 KH 0ppm, no supplemental CO2, no other buffers, and you added 1 dose Seachem acid buffer and 1.3 doses Seachem Alkaline Buffer, what would be your pH? What would be your KH? Why?

Assuming an inevitable quantity of some CO2 in the water but no CO2 injection, the pH would be 6.5 and the KH would be about 0.5 dKH.


4) Another way is, for a given CO2, how can you raise the alkalinity with a bicarbonate, but keep the pH at 6.5?

Add an acid along with the bicarb.

5) Is the product at pH 6.5 a buffer or a pH up/down product? Why?

It’s a buffer. It buffers the water and resists changes in pH upon the addition of acids.

Does anyone at Seachem have a tank with pH 6.5 and "buffered" with Seachems buffers? If so, what is their KH?


The planted tanks here use tap water for the most part. No need to buffer it and it comes out a pretty good pH for the plants. We do have a couple of tanks using RO/DI water that are buffered using only Alkaline Buffer. pH is below 7. Not sure what the dKH is. To be honest, we perform frequent enough water changes that buffering does not seem as necessary for our situation.

Thank you pointing out the chart error which I have changed to KH 4.0. at pH 7.8.

You’re welcome.

[Cardinals]

Well, if water with a KH of ~0.5 or ~9ppm HCO3- is "buffered" we should start rewriting the chemistry books!
But seriously, why don't you prove me wrong, and Seachem right, grab one of your tanks, (remove all phosphates with phosgen, an excellent product btw) and add 1.3 doses Alkaline Buffer and 1 dose acid buffer. Measure pH/KH daily and let me know the results?

[QUOTE=Tech Support JS;4911]
An exceedingly high KH (8,10,12) will cause ionic imbalance, while a low one (0.5, 1), in your case, would probably indicate inadequate buffering. Your KH will prob. be on the low end, ~2...[/QUOTE]

[pamdaly]

This is my first post and I hope I am correct in posting a reply in this thread versus starting a new one. My questions also have to do with the pH, KH, and GH relationships. I am most appreciative of all I've learned from your postings.

Here's my situation:
29 gal freshwater community tank with mod. to heavy planting. 17 fish are:
5 Cherry Barbs
4 Red Phantom Tetras
5 Blue Harlequins
2 Blue Rams
1 small Pleco

Lots of driftwood, a sponge filter and mechanical filter with carbon pouch, temp kept at about 80 d.
Ammonia 0
Nitrite 0
Nitrate 5
KH 13
GH 11
pH 8.2
water source: East Nebraska deep well - known to be "hard" water (Phosphate: 0) I change out about 4 gal. of water once a week and use Prime at that time. One of my original 3 Blue Rams died - cause unknown but possibly protozoa - treated in hospital tank for one week with Metronidazole but died. Remaining fish active, eating and colorful.

For two months, I have been trying to get my pH down. Actually, I have decreased it from 8.8 to 8.0 - 8.2 but would like to get down to 7.0 - 7.4. I've used acid buffer (1/4 t every day for 2 weeks and lots of driftwood). I've avoided using any other pH down chems knowing my KH and GH are so high and not wanting bounce. I want to get the pH down GRADUALLY and as naturally as possible. I have ordered some peat to put in the filter but believe it may be too gradual or not really effective given hardness measures.

Having recently tested the KH and GH, I'm aware I have a big problem here and want to proceed very carefully. My store expert finally recommended I try mixing RO water with my well water for my weekly changes. I bought 10 gal of RO and am currently just aerating it. If I did this, I would be putting 2 gal of well water and 2 gal of RO in the tank each week. My questions are:
1. Would this eventually bring down the pH?
2. Would it bring it down safely? That is, no huge bounce at some point.
3. Would the high mineral content of my well water preclude the necessity of adding something like Seachem Equilibrium? Would the addition of this product hurt anything even if it's not entirely necessary?
4. Should I continue to use the Acid Buffer while using the RO water in weekly changes?
5. Should I go ahead and use the peat while doing the above?

Finally, I've converted my hospital tank to what I call my "Experimental Tank." If you don't feel comfortable saying with certainty that the above plan using RO is safe and gradual, I could make controlled additions (with measurements after each) using the Exp. Tank. It is 10 gal. and I currently have it set up to establish baseline measurements: it contains 5 gal. of well water with a mechanical filter going. This morning its measurements were :
KH 15 (2 drops more than the main tank)
GH 11 (same as main tank)
pH 8.4 (.2 higher than main tank)

Expert advice from anyone in this thread will be most welcome.

[LabTest57]

1) You should know that well water can contain a lot of protozoa, parasites, depending on local and/or state sewage management (water containing trace amounts of human feces can get into contact with a well if it doesn't meet certain standards - you can google this.) Before I add well water to an aquarium, I treat it with chlorine (at ~4 ppm) for at least 3 hours, then I dechlorinate the water.
2) If your going to lower your PH, lower it slowly everyday (you can cause pH shock to your fish).

3) Your GH seems to be fine, however, your kH should be in the 4 to 6.5 range. The best way to accomplish this instead of using RO water, is lower the pH of the water you add to your aquarium (when making a water change,etc.) to the desired range and let it sit for about a day. In your case, I would get a tank that is close to 30 gal or maybe half of it, and do the water change (pH lowering) method mentioned above; in other words, you can do a 25% water change every other day with water at a lower pH until you get to the desired pH range for your community tank.

[LabTest57]

Some specific amounts of sulfuric acid or pH Down (sulfuric acid), in most cases its dry acid a.k.a sulfuric acid. I use muriatic, but at way lower quantatities (drops) =).
__________________________________________________________________________________
For every 5 gallons of water, and assuming your Kh is ~300 ppm and Gh ~260 ppm from a max. flux effect, I would say you can add ~0.05 ounces of sulfuric acid to get your pH in the 7.0 to 7.8 range; however, 7.0 to 7.2 will temporarily show up on test kits until the water is settled or agitated for about a day.

On a 29 gal. tank, to lower the pH dramatically and temporarily to 7.0, add 0.3 ounces of sulfuric acid or pH down. Since you have a large amount of fish for such a small tank, the temp. effect could last for a few days (3-4), and for a mod. to heavily planted tank you can expect your pH to rise (IF your plants are FLOURISHING and not dying). The rise in pH can be slow though.

For "drop measurements" of pH Down or sulfuric acid: add 180 drops for every 30 gallons of water, or 30 drops per 5 gallons of water (assuming your still using well water with a kH of 13 and GH of 11 and pH of 8.0 to 8.4).

[LabTest57]

[QUOTE=LabTest57;7127]For every 5 gallons of water, and assuming your Kh is ~300 ppm and Gh ~260 ppm from a max.[/QUOTE]


Correction: I thought you had 15 kH, for 13 kH it would be ~0.035 ounces per 5 gallons of water.

For drop measurements its 21 drops per 5 gal. of your well water.

Note: you can test and lower the pH anyway you want, to gradually acclimate your fish to the target pH of 7.0 (or range of 7.0 to 7.4). I'm merely giving you some instructions on lowering the pH via acids. =)

[pamdaly]

Dear LabTest57,

Thank you for taking the time to share your knowledge with me.

A few more questions:

1. How gradually should one decrease the pH? I'm in no hurry and don't want to stress the fish. .2 degrees a week?

2. I had avoided using chemicals to decrease the pH because I was afraid of pH bounce. If I take your route, is there a possibility of this and should I use buffers to avoid it?

3. What pH down product would you recommend?

4. You dismissed the RO route. Is this because you don't think it will work or that it is too much work/expense/ or what? My thinking was that its purity when combined half and half with my well water would have benefits in addition to bringing down the pH: e.g. lower the GH. I do have 10 gallons of it sitting beside my tank that I was thinking of using in my 10 gal experimental tank.

Again, thanks for taking an interest.