stupid question about rain

[Waterbug]

The pH of rain in NJ averages about 4.5 but can be down at 2 or 3 during thunderstorms. Rain is naturally a pH of about 5.3. For comparison vinegar is about 4.5 pH. If you had say a 10'x10' pond and 4" of rain per month that would be like adding about 250 gal of vinegar every month.

If someone asked if pouring 250 gals of vinegar into their 10x10 pond would be a problem there would be a lot of danger warnings about killing fish. But the same acid strength in the form of rain, no big issue. Strange world we live in.

Measuring pH after rain is also kind of strange since if there was a pH crash the pH test at best would only tell you dangerous event happened, in the past. Plus a pH crash will also result in pH swings, So you could test pH and see 8.0 and think everything is good and not realize in an hour it could be 6.0.

Testing KH on the other hand can tell you advance if a certain amount of rain is going to produce a pH crash. To me that seems a bit smarter.

Oyster shell
The substance in crushed oyster shell related to pH is calcite which only becomes water soluble when the pH is under about 7.5. That's pure calcite. Oyster shell has other elements which slow the access to calcite. These two things make oyster shell very slow to react with acid. And thank goodness too. If oyster shell did dissolve in water above 7.5 oysters would have a pretty serious problem and oyster shell would not exist.

Yes, oyster shell will bring pH back up from acid levels, but that can take a couple of hours, after the pH crash. And it takes a lot of crushed shell. If you scale the amount people use in aquariums to a pond you'd be talking about several tons of crushed shell.

The stronger the acid the faster the oyster shell will react. This means lets say 7.2 pH water could take days or weeks to get to 7.3.

There's no down side to adding oyster shell. It doesn't harm a pond one bit. And if your water is already say 125 ppm KH or more, and you don't have a high fish load and you want to believe your little bag of oyster shell is responsible for stable pH I say good for you. Tell the world and try to convince as many people as you can. It's what the internet is for. It's the buyer's responsibility to research I say.

But for the few people who's pond has low KH and/or high fish loads, or don't do water changes with 100ppm+ KH source water, and don't test KH AND think oyster shell is a good pH buffer...you could be in for a truck load of learning the hard way.

 

[addy1]

Well all I can say is our water reads almost zero in KH, with adding oyster shells every spring the KH is around 100. For me working.

 

[taherrmann4]

Addy do you just dump them in the pond?

 

[addy1]

Addy do you just dump them in the pond?

I put them in the bog where there is constant water flow over them. They are usually gone by the time I shut down for the winter.

 

[taherrmann4]

Great thanks.

 

[Waterbug]

Well all I can say is our water reads almost zero in KH, with adding oyster shells every spring the KH is around 100. For me working.

You should write it up and publish because it would change fundamental laws of physics and you could win a Nobel Peace Prize. That would be cool.

 

[capewind]

WB, I have a KH question for you that I havent asked yet, but Addy's response made me think to ask it ... Hubby was the one to deal with the KH in the pond (he uses crushed coral til I wanted to try baking soda) but after *I* started learning about KH, I started testing my TANKS with the strips (I know the strips are not reliable, but hubby was out of KH/GH test liquid and all I could get at the store were strips) .. One tank was irrelevent as I had some coral in there to bring up the PH ... another tank had none ... my tap water tests very low (on the strips the results were 20-40 ppm, doesnt register with the drops) ... without adding anything, the KH in the tank came UP to the 60-80 ppm range. WHY???

I know outside, first thing in the spring when there's the short term algae bloom (and time to normally add coral), the more algae, the lower the KH drops ... I understand that the algae uses the calcium .. but the chemistry I am stumped on is how it can come UP inside???

My tap water also tests at 7.0 ... both the pond and tanks, the PH tests at 7.4-7.5

 

[addy1]

You should write it up and publish because it would change fundamental laws of physics and you could win a Nobel Peace Prize. That would be cool.

All I can say is my pond tested KH 35 range, I put in the crushed oyster shells, the water is now 107 per drop count, same test fluids, same test tubes, same water, i.e. pond. For me it is working
PH a nice 7.6 or so, with tons of rain falling. Rain lower than 6 I feed our gutters into the pond, it has been flushed well, i.e. water change over, ph still a nice stable 7.6

 

[capewind]

Addy, my intent is not to question what is working for you, but WHY, in a controlled environment, such as a tank, with nothing added to increase the KH, it comes up???

 

[addy1]

lol I know capewind. WB wants me to write it up, get a peace prize, no thanks. Just mentioning that it works for me. At this stage in life, I could care less, if it works I use it, if it doesn't I don't.

 

[Waterbug]

One tank was irrelevent as I had some coral in there to bring up the PH ... another tank had none ... my tap water tests very low (on the strips the results were 20-40 ppm, doesnt register with the drops) ... without adding anything, the KH in the tank came UP to the 60-80 ppm range. WHY???

That's not really enough info to make a guess for this specific case, but I assume you're asking a more generally question...why does KH go up without adding anything?

First, the easiest to understand is like you said, test strips. And really even drops can be difficult to get real accurate readings. The difference between 40 and 60 ppm is not that much. Throw in some poor testing procedures and I probably wouldn't trust those exact ranges too much. But, lets put that aside and assume the test results are accurate because they well could be. Just wanted a disclaimer in there.

Simple answers
There are none. Generally we don't really need to know the whys. We generally only care about ranges. Once we know how to maintain a range that's good enough. The causes of why KH goes up, or even down, are pretty complex (at least to me). Same with pH.

Step one is to remember KH is measuring the capacity of water to neutralize acids. Sometimes we say KH measures the amount of say baking soda in water. But that's not exactly true. And if you think of KH as that you will indeed wonder how KH went up even though nothing was added.

So, take the case of oyster shell. It will neutralize water below say 7.2 pH. But that won't be measured by KH. The reason is because KH is measuring the capacity of water to neutralize acids, not the capacity of oyster shell to neutralize acids. It's an important difference. Instead the only way to measure the capacity of oyster shell to neutralize acids is to place low pH water in with a certain amount and size of crushed oyster shell and then measure how fast the pH rises. Very different from KH.

It's this concept of adding something to effect KH that can be misleading. Because in ponds and aquariums about 100% of the time when we talk about KH we're talking about adding something. We lose track that KH isn't measuring what we added.

By "nothing added" we mean we didn't dump anything into the water and we didn't see anyone else dump anything into the water. But someone did when we weren't looking, and even if we were looking we wouldn't have seen it because it's Mr CO2. And Mr CO2 in water is an acid. And acid drives KH level.

And there are lots of minerals that react with each other as temp and pH change. That's the complexity. There are acid buffers and alkalinity buffers all working together and against each other. Makes it pretty difficult to point at any one thing.

The best sources for simple info is provided by aquarium keepers. They've read the complex stuff and made it a little more simple. I don't know of a single best source, but many are pretty good. If you read several you might get some basic insight into possible reasons your KH increased. But in general they're not going to go into why KH increases on its own, they don't really have a reason to know. It's the same as we don't really need to know all the reasons pH moves between 8 and 9, only that it stay in that range. KH is the same deal.

Complex but more precise answers
There are just tons and tons of info on the subject. Unfortunately the good stuff takes a long time to read and understand, but it can be done. Here's a pretty good paper on one aspect of how KH moves. I know it's overwhelming, at least to me it is. Here's how I approach it:

1. Skim the entire paper. I don't know 90% of what their talking about, that's normal. The purpose of these kinds of papers is to convey data and procedures in detail, like a blueprint. They are not meant to teach a subject. Normally there's a conclusion at the end which is normally very understandable. The goal of skimming is see if you think this could be related to whatever you're wanting to know.

2. Now that I have a basic idea of what the paper might be about I go back to look for is the specific parts that are about the subject I care about. There's almost never going to be a paper that describes exactly what you're after and only that thing. Like when I read a paper on concrete sewer pipes I only care about the effect of pH on concrete. The other 95% I skip. So in total these papers can seem overwhelming but generally most of the what you're after is just a few paragraphs and a few tables.

3. Once the section of interest is found you tear it apart. If that takes looking up every single word and spending hours learning a single term then that's what it takes. Ya gotta be interested (obsessed) to do it that's for sure.

4. Give up. It's tooo complex. Then come back to it in a month, a year or whatever. Each time you'll pick up a little more.

 

[capewind]

Thank you WB. I will check out the link tomorrow when I can focus (when everyone is working). This will make very little sense, but on a lot of topics, I can not comprehend the most basic simple answers, I NEED the more complex explaination for the "simple" to make sense to me. In a lot of cases, I need those WHY questions answered.

I do understand that there are many complex reasons why KH drops, but the most SIMPLE answer to me is when it happens in the spring (with an explosion in algae growth), algae is using more "calcuim" for the most basic of explainations (faster rate of consumption). I NEED the chemical explainations, without getting dizzy;-) Like you said in #4, give up and come back later, to gain better comprehension.

Irrelevent analogies, but I can LOOK at a large dog, and without seeing xrays, can judge the confirmation to the extent of projecting with high accuracy of whether that dog would develop hip dysplasia. Or with a horse standing still, the length and angle of the pasterns, I can predict their gait. Just like most folks can say that because "dark clouds" suddenly moved in on a beautiful day, it is likely a storm brewing. There are signs to many things, and gaining more complex knowledge puts us into a better position to play the probabilities to our desired results.

 

[Waterbug]

I like the whys too.

Here is an aquarium page that does a really good job imo of the very basics of alkalinity using specific chemical explanations. It's more related to ponds so maybe a little more interesting.

I think if you wanted to answer the question, "how can KH increase on its own", you would have to start with the KH test itself. What kind of acid for example is the reagent? What kind of color indicator chemicals? I mean you have to start some place.

Of course this will all lead you to the real complexity. Like for example... Yes, algae growth and death affects alkalinity and you can figure that all out. Yes, bacteria growth and death affects alkalinity and you can figure that all out. Yes, there are bacteria that produce carbonate...on and on. Then you have to figure out to what degree each of these is affecting alkalinity. Did your KH rise because you have carbonate producing bacteria? Starts getting really tough to answer. I'm not even sure an answer is possible. Best you could do is better and better understanding of the possibilities. Certainly in the real world it would be way, way too expensive to actually know the answer for a specific sample of water from something as complex as a pond.

That's why we generally just stick to the big picture and just measure KH and track it and adjust it.