Ph Fluxuation? How to control?

[GreatDanesDad]

Pond and filter: I have a 2000ish gallon pond. A double waterfall and two pumps. First pump is 3000gph to a bio-filter and then over the waterfall, and the second is 1200gph running through a second bio-filter with a UV and then back into the pond without a water feature.

Environment: Temperature is 87 deg. (Ya it is hot in Arizona). Ammonia ~0. Nitrite ~0. Nitrate ~2ppm. Kh ~180 ppm. Ph in the morning 7.4 in the afternoon 8.2. The PH is bothering me. I have checked 5 days in a row and it is very consistent. I have read many time .3 is the largest safe change.

Fish and Behavior: I have 10 Koi equaling about 80 inches. I am seeing my 8 smaller fish flash occasionally after eating. They all do it once or twice in a 15 min time frame and only after eating have I seen it. You have to sit and stare and be very focused or you would never see the behavior. Maybe I am being hyper sensitive. With all my reading on the subject, it points to a water issue if the bulk of the fish are showing signs of irritation. I looked at 2 fish under a scope, don’t see any mites.

Plants: The water is very clear so no floating algae. There is algae on the sides of the pond. It is about 1/8in thick uniformly and has recently started growing long strings. (I would love advice on if this, is ok or should I scrub it or should I get an Algaecide) I have two mid size lilies and 5 or so cat tails. The plants are in three corner of the pond and are planted in 2 gallon buckets. In my opinion not many plants.

So here is the question I have tested for almost a week and see that my pond is repeatable. The chemicals are close to the optimal values except the swings of my PH in a 24 hours time frame.

What can be done to stabilize my pond Ph swings to ~.3 instead of ~.8, or am I being hyper sensitive?

 

[crsublette]

I would push your KH up higher, very well above 200 and dose the water with some calcium and that will fix the pH swings, explained in remedial water chemistry and treatment.

The growing algae is quite likely consuming and releasing inorganic carbons, that is carbonates, bicarbonates, and carbon dioxide, that is causing the fluctuations in the pH. So, if you can reduce the algae, then this will make a difference.

In regards to attempting to control the algae, I get a little bit more complicated with an oxidizer, as is explained in the hyperlink above, but, if you want to use something that is safe, then Algae-Fix will work; follow instructions precisely to the letter and be sure you know your exact pond gallons, within +/-50~100 gallons. Other than this, you can try puting more plants and improving your bio-filtration and add more aeration to the pond or simply just a bit of elbow grease.

 

[Waterbug]

Ph in the morning 7.4 in the afternoon 8.2.

That's a very normal diurnal shift. You can Google "diurnal pH shift" for more info.

What can be done to stabilize my pond Ph swings to ~.3 instead of ~.8

You could double check the KH reading, but that's a pretty easy test to get right. I assume it's correct. I did expect a higher pH range for a KH of 180 ppm, so I'd be double checking things. Warmer water does decrease pH, but at this temp range I didn't think temp would make much difference.

Your KH level is good. You could increase that to whatever level you like, 200-400 ppm would be fine, even more. I doubt you'd see any change in the diurnal pH shift. At some point you'd see pH increase to higher levels, but you'd still probably see a diurnal shift, just at a higher level.

GH also can affect pH stability. Most pond keepers don't screw with GH. Almost no web sites explain it, I assume because they all just copy stuff off other web sites. GH is often skipped because it's normally fine, it isn't consumed like KH. And most people don't see a need for a tighter pH range GH can provide. In a nutshell KH can be increased with something like baking soda so pH increases into the 9-10 pH range. But GH stops it from going about 8.4. So you have one thing always ready to push pH higher and another stopping it at 8.4 and the result is pretty stable.

GH measures magnesium, and other minerals, which is important to fish. So measuring GH doesn't hurt.

Here's a good page on pH. I don't agree 100% with everything on the page, but the chemistry is good.

or am I being hyper sensitive?

That's purely an opinion call. You can find lots of people who would not worry about that pH range and KH level. You can find lots of people who think the range should be tighter, like 0.5 or 0.3 or whatever number someone wants to pick out of thin air. Some people think Koi and Goldfish require a tighter pH range their wild cousins. On, and on.

I'm not aware of a single study that shows any harm to Koi and Goldfish in your pH range and KH level. It's extremely rare for any pond info source to cite any kind of anything. Easier to just make up stuff.

 

[crsublette]

The fluctuation of carbon dioxide is the typical, not only, root cause of diurnal pH swings. As the pH increases due to increased alkalinity, then carbon dioxide is less able to promote a diurnal pH swing.

"Diurnal" refers to any cycling pattern, such as the sun rise and sun set increasing and reducing plant and algae photosynthesis and respiration. The volume of alkalinity and duration period of photosynthesis and respiration indicates the extent at which these entities will create a diurnal pH swing.

Once alkalinity reaches its natural setting point, in our context with using baking soda which is bicarbonate, is around 8.3~8.5 (due to the pKa value of the hydrogen ion in bicarbonate, HCO3-), then the likeliness of there being a diurnal pH swing is significantly reduced. From this point, only when nature produces hydroxides, or removes a hydrogen cation, which increases the carbonate concentration, will there be any type of pH swing. In this situation where the pH raises above 8.3~8.5, it is the calcium cation concentration that neutralizes the swing, in which GH is not a good indicator of calcium presence. GH can still be quite high due to all of the divalent minerals while calcium concentrations are still quite low.

Everything is in equilibrium in the water and the concentration ratios change according to many variables especially due to a change in alkalinity and pH. As the pH of water increases, then the concentration of carbonic acid is reduced. To get a better idea of the pattern I am talking about, then google "freshwater carbonate speciation diaghram"; the pattern changes according to many variables, but this will give you a visual sense of what is happening here. To help understand further this diaghram, this type of diaghram is called a Bjerrum plot.

 

[Waterbug]

The pH of baking soda is 9.

 

[crsublette]

The pH of baking soda is 9.

I'll be the first to say I am wrong, but you'll have to put a bit more effort into it. I know that's not how you prefer to do things due to your obvious one-liner, but, as I said, I am glad to be shown how I am wrong and will admit to being wrong if I am wrong. To be otherwise, it would be quite childish.


Actually, depending on the product, if you round it up, then, yes, it is 9.

In particular, I would love to read the henderson-hasselbalch equation for sodium bicarbonate you are using to suggest it has a pH of 9, that is food grade found at the grocery store, with the known molarity of the concentrations used in solution, and if there is presence of carbonate (CO32-), if it is an aqueous solution. This is something that has to be done mathmatically, unless in a lab, due to how a even minor introduction of carbion dioxide to the fluid will increase the carbonate concentration. When introduced to water, even just 1mg/L of CO32-, which isn't much, will offset of the pH to be higher. As far as I understand, when preparing aquaeous buffer solutions, this has to be taken into account in the explanation of the pending pH.

For example, the MSDS for Arm & Hammer baking soda indicates a 1% solution of, no molarity of the concentration mixed into solution is shared (all is shared is the molecular weight), has a pH of 8.2.

 

[crsublette]

To help folk further understand, 10 ml of 0.1 molar concentration of sodium carbonate (Na2CO3) mixed with 90 ml of 0.1 molar concentration of sodium bicarbonate (Na2HCO3) will increase the pH of solution to a 9.2 pH at 68*F (20*C).

To further understand, here is a reference to a table when creating your own carbonate/bicarbonate buffer solution.

If the concentration of carbonate (CO32-) were reduced, then the pH would be significantly reduced.

In our context, of a freshwater pond environment with presence of the divalent mineral, calcium (Ca++), simply just a low volume 20mg/L of Calcium will neutralize the small amount of carbonate produced by nature. However, if nature's presence significantly increases due to heavy algae presence, ammonia presence, and other variables, then the production of carbonate is increased to the point where 20mg/L of Calcium will not be enough to neutralize the production of carbonate. Thus, the pH increases closer to 9 and higher. As nature's presence increase, then so does the concentration of calcium needed to neutralize it.

When baking soda is very significantly heated, that is above boiling point, then the solution starts to break down into a carbonate solution.

In particular, when buying the KH products at pond stores, these products contain a mixture of cooking baking soda (that is carbonate) and regular baking soda (that is bicarbonate).

Even manipulating the concentrations of NH3 to NH4+, this can create a particular buffer solution, which is another reason why in our context, baking soda will have a lower natural pH of around 8.3~8.5, depending on carbonate and calcium concentration.

So, it is quite misleading and simply not true to even suggest that baking soda has a pH of 9, which is quite likely something you read from reading the small text notations in a google search and an example of how poor googling results to bad information.

Context is extremely important.

 

[sissy]

I just use crushed oyster shells to stabilize ph

 

[crsublette]

I just use crushed oyster shells to stabilize ph

It does help to an extent, but not as much folk think it does help. The particulate size, how water is flowing through it, pH of water, and volume of product is what determines the products effectiveness ranging from "helping some" to "helping not at all".

It is mostly used in aquariums due to the fact the product ratio to water volume is quite high.

The product can be so ineffective that there were carbon dioxide reactors created so to increase the products effectiveness. These reactors create an abundance of carbonic acid, which dissolves the calcium carbonite product. These devices are used for many other mineral products as well. My version of the explanation to help you further understand the mineral product at how it contributes to the water.

Sissy, I am not saying it is not helping you, but you are likely overestimating its effectiveness. In your situation, reading how things are in your pond from your posts, I think the high organic content of your pond and the low fish desnity are what are also a big part of helping to stabilize the water, while the oyster shells do what they can do as well.

 

[sissy]

I have it in laundry bags and use a whole bag of it in both filters and in the waterfall area .PH has been stable for over 3 years now and even with the torrential down pours we have been getting every day .Just tested the water and so far so good .It is still raing out heavy and has been since 3:30 and it is now 6:45

 

[crsublette]

Yep, I am not denying it has an impact, but you have to take into consideration your entire pond's context, which involves more than just the oyster shells being present.

 

[crsublette]

In our context, of a freshwater pond environment with presence of the divalent mineral, calcium (Ca++), simply just a low volume 20mg/L of Calcium will neutralize the small amount of carbonate produced by nature. However, if nature's presence significantly increases due to heavy algae presence, ammonia presence, and other variables, then the production of carbonate is increased to the point where 20mg/L of Calcium will not be enough to neutralize the production of carbonate. Thus, the pH increases closer to 9 and higher. 1) As nature's presence increase, then so does the concentration of calcium needed to neutralize it.

1) As nature's presence increase, then so does the concentration of calcium needed to neutralize it.

I am in particular referring to the various actors in the pond that produce hydroxides, which then create the carbonates.

In ponds that are better maintained through particulate filtration, ammonia production is much higher and managed by aerobic oxidizing processes, and water is very well circulated, then the natrual tendency is for the pond's pH to go down due to ammonia oxidation and this will consume more calcium carbonate.

However, in ponds where the organic presence is higher (which organics are more complex to decompose), fewer aerobic processes to reduce ammonia, and there is some ammonia production by fish, then these ponds will have a natural tendency to go up due to nitrate oxidation from organic decomposition, plants or algaes, and this causes the pond to produce more calcium carbonate, if proper free soluble calcium is available. In higher pHs, the calcium in the calcium carbonate products is quite insoluble.

So, the chemistry of ponds will differ from each other, which shows another reason why pond's context is very important and how it changes the efficacy of particular products.

 

[sissy]

There are lots of things to consider true .How many fish and feeding them is important .That's why I feed mine 3 or 4 times a week it makes it easier for me and i think healthier for them .There is no magical formula out there for a clear pond that you can buy .Takes time and learning .I wish I could wave a magic wand and make it easier sometimes .