high PH

ste1957May 9, 2012

Can someone help me lower my ph in my fish pond? I have a 1000 gallon fish pond and the ph levels are always high night and day, I keep putting in ph decreaser and nothing happens. I am on a well system water supply and the ph straight from the well is 7.5 but when its in the pond it goes to 9.0 and higher.someone told me to pull the lime stone rocks i had in there because they said the limestone was raising my ph. So i did and there still is no change after 3 weeks and adding more ph decreaser as well. My water also turns green but i do not get any string alge. Please Please Someone help me!

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I am wondering if you have something else in your pond? Perhaps some poorly made cement blocks or something else? Unfortunately, I have not had your problem. I am also on a well which makes things easy for me. It is always possible that your test kit is off, although showing a 7.5 pH for the well water makes me think it is probably working.

If you haven't done some water exchanges, it isn't surprising that your pH hasn't come down yet. The general rule is not to change everything all at once, so unfortunately you will have to pump some water out (maybe 20%) and add some back and then do it again and again etc. over several weeks.

You didn't say what your pH reducer was. Usually, people who have problems just throw a couple boxes of baking soda in the pond. That would bring the pH to ~8.3 from low or high.

    Bookmark   May 9, 2012 at 7:37AM
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Ste 1957,

The reason the tap water is 7.5 ph is because it is very high in CO2. Once it is exposed to the air for a while the CO2. drops and the PH goes up to it's natural PH. Most of the well water in Illinois is 8.35 and I would guess that is what your pond PH is actually. That a glass of tap water and let it st for 24 hours and test the PH again and see if it is the same as the pond. That will tell us if there is something in the pond raising it higher than what it should be. Stop using PH down as it does work you will not be able to control the PH. If you live very close to northern IN then your natural PH could be higher. I would careless about your high PH and more about what else could be in the water. Never just put the hose in the pond when adding water. Always spray the water though the air and let it in the pond like rain.

    Bookmark   May 9, 2012 at 7:56AM
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I have done water changes and same results. How much baking soda would you put in. My pond is 1000 gallon. I have no other rocks in water. It is a black rubber liner that I bought at pond store. I have had this same problem for 4 years now. I will do test with water sitting for 24 hours and repost results

    Bookmark   May 9, 2012 at 1:49PM
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buyorsell888(Zone 8 Portland OR)

Consistent high ph is better for plants and fish than constant ups and downs. Messing with ph is often worse then leaving it alone.

If your plants and fish are fine there is no reason to worry over a test strip....

    Bookmark   May 9, 2012 at 3:43PM
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In the high desert everything from water to soil to rocks has high PH. My pond is starting it's second year and my PH has always been high. I talked to the local pond shop and their's is the same as mine which they say is normal. Mine measures 8 in the mornings and 9 in the evenings. I used vinager to lower it last year but decided this year if the plants and fish are fine (which they are) I wont mess with it. My pond is doing great so I am not concerned. The only thing you should watch for is high amonia as high PH can make amonia spikes worse. So test your amonia and if it tests 0 don't worry (mine has always tested 0).

BTW, I have also heard that adding PH down can do more damage than good. Be very careful what you add since many of those chemicals can turn a small problem into a bigger crisis.

    Bookmark   May 9, 2012 at 4:00PM
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Goldfish and your plants do not mind the high pH. Most of us add sodium bicarbonate to buffer the water from drastic pH fluctuations and it brings the pH to somewhere close to 8. I would not worry about testing for pH but test for general hardness dH and carbonate hardness KH. Fish and plants need minerals like calcium and magnesium to build bones, scales, etc. If your fish can live in the water and look normal, I would not worry about it.

    Bookmark   May 10, 2012 at 8:07AM
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Did you check the well water like mike_il suggested? If it reads 9 or over (after setting), then either your test kit is a little off or that is its natural condition. I have never heard of water with a ph over 9, but there are plenty of things I haven't experienced.

If everything else seems ok anyway, I think I wouldn't worry either, except that I was a chemist for 35 years and would find a way to check it out to see what I was drinking. If you are still concerned I suggest you find a friend who is a chemist/biologist or knows a chemist and ask them to get you a little bit of test pH paper in the range you are checking and email you a pic of the color code.

I was suggesting using one or two store size boxes of baking soda. You could throw the unopened cardboard box in there. But again, I haven't needed to do it. Well, actually, to enforce the point, I don't know either. I'm not working in the lab anymore and I can't guarantee that the test kit I purchased is accurate either. It says pH 8, and I am happy, but who knows?? I didn't take water to my old lab with fresh standards etc. etc.
My fish, frogs, birds, and plants all appear fine and my water is always clear. I atribute All of this to my long attached stream.

    Bookmark   May 10, 2012 at 7:51PM
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The ph was high after sitting 24 hours. So what's next? My water gets dark green. But I don't get string alge. Do I treat my water alkalinity first and that will correct my ph. Or do I get ph in line and it will straighten up my alkalinity ? Please advise. My plants seem to bE growing as well. Also I have my pump in a container at opposite end of waterfall with a piece of filter over the top of it to filter water along with the green filter pads in my bio falls. I clean both filter once a week. Is that ok? I'm using phusion ph decreaser.

    Bookmark   May 11, 2012 at 1:51PM
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Hello ste1957.

I can't help with your specific ph issue, but there are many here who can and you've been offered some good advice.
Water tests can be a valuable tool but the very BEST they can do is provide a CLUE to diagnosing a problem. Attempting to 'correct' the ph of your pond based solely on a test is a bit like attempting to treat a fever without knowing its cause/underlying illness. This can result in more harm than good. Don't.do.it.

Let's back up & regroup here and get to the root of the issue. A couple of questions...

QUOTE: I have had this same problem for 4 years now.

What problem is that EXACTLY? You say your plants seem to be growing. Are your fish thriving or are you experiencing problems with them? What prompted you to test your water to begin with?

QUOTE: My water also turns green but i do not get any string alge.....My water gets dark green. But I don't get string alge.

Ok, so WHEN does this occur? Is it a an ongoing problem or a seasonal one? In other words, do you have green water all the time OR only when you start up your pond in the spring? Your pond is 1000 gal. What's the ratio of fish:plants:water? All of this info is necessary in determining the source of your problem IF, indeed, you have a problem.

I say again: What prompted you to test your water in the first place?


    Bookmark   May 13, 2012 at 2:25PM
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Thanks for your concerns as well as everyone else. So my problem is that I have green water. Pond stores say its.B Ecause of high ph. I was told I need to correct my ph first. Well I treated it with phusion decreased. My ph stay at 9 or higher. I want clear water like every other pond I see.i drain it every spring because of lot of leaves that fall in in the fall. Water is green after about 1 month. And stays green. Not Clear. Plants do not always do good in pond either. Some of my Lilly pads leaves are starting to due. I have about 20 small gold fish in pond. I did a 25% water change 2 weeks ago and nothing changed. I have my pump in a container with 2 filter pads over it and then it goes into. Io fall which has 2 pads. Some say to clean. Other every week some say clean it 2 times a year. I have to clean them every week or else they came up with thick green muck. I was going to get abox of ATM n hammer and throw it in. I will wait untill u post something. Please help.

    Bookmark   May 15, 2012 at 9:47PM
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From your info. it appears that your fish and plants are alive, as are you, and you are all consuming the same water. If it weren't for the green, I don't think I would worry about it. I don't remember hearing that high pH encourages alge but I don't know. I also can see that people have had problems and struggle for long periods to solve them.

I can tell you that plants placed such that their roots reach circulating water in crevices will collect crud that helps them grow. Theoretically (at least) the plants compete with the alge for nutrients. I have a dramatic example with a 25 foot stream with so many plants that it looks completely natural. So natural that without some plant removal, the stream is hard to see from some views. Last week, I removed 2 overgrown clumps of sweet flag. They came out with great gobs of mud that wasn't there when the small clumps were placed in the rocks in the stream. Unfortunately, equally great gobs were disturbed and flowed downstream into the pond. The pond turned into a turbid brown and the fish were almost completely obscured. However in several hours, some muck settled and the rest got recirculated and attached to the rest of the stream root masses and the pond became chrystal clear as always.

I have had some string alge that now mostly resides in the stream helping to catch crud, but I have never had anything but clear water. I do have a skippy but as far as I can tell, it isn't doing anything. Nothing is caught in it, the sponges all the way down are completely clear. Perhaps it does have bacteria, but at times when it wasn't in circulation, the water remained clear.

Therefore I would suggest that if you have (or could create) a shelf in the circulating water, that you make sure that it has a lot of plants, some of which are in crevices or between pots so that their root masses are free.

    Bookmark   May 15, 2012 at 11:21PM
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waterbug_guy(Phoenix AZ (Melrose))

Green water and pH are unrelated. Let me guess, the person who told you this also sold you the pH decreaser?

Buy a UV filter to get rid of the green water. It is 100% effective when installed correctly. Clears the pond in 3-5 days. Tons of other ways, but all are hit and miss at best and many are just plain dumb.

It's not surprising you have no string algae. Different species of algae produce allelochemicals to kill competing algae and also heterotroph bacteria that attack the green water algae. Once your pond is clear you will probably see string algae at some point. At any rate, normally a UV only has to run for a few weeks to give string algae and green water killing heterotroph bacteria a chance to get the upper hand. After that most ponds will stay clear for months or years without the UV.

If you're ever interested in messing with your pH there are 2 tests that are more important, KH and GH. You can Google "pH buffering" for more info. Baking soda raises KH and that keeps pH above 8.3, but it can go higher. Calcium chloride flake (deicer) and magnesium (Epsom salts) raise GH and precipitate out the baking soda above 8.3 pH so the result is stable 8.3 pH. There are other ways to stablize pH at different levels, but the 8.3 method is pretty easy and cheap. And there are always other factors.

Adding the pH decreaser is an excellent way to kill all the fish.

    Bookmark   May 16, 2012 at 2:29AM
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Where about in IL do you live? Most of the well water in IL comes from limestone so the PH is going to be about 8.35 and is going to have a hardness of 425 ppm and alkalinity about 425 ppm. All of these will be just fine. Waterbug guy is correct the only way to be sure to get rid of the green water is a UV. String algae is going to start to grow and if the bacteria in the pond isn't disturbed the algae will come under control in about 4 years in this area.

    Bookmark   May 16, 2012 at 10:12AM
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How are you determining your PH? I hope you are using a liquid test, not the test strips. Those are essentially useless.

That being said, last year for the first time in about 4 years I was experiencing massive PH fluctuations. Baking soda has been discussed, and it's an excellent solution (short term). Use a box (big one). It CANNOT lower the PH 'too low' and it's not harmful to the fish.

If possible, mix the baking soda in a 5 gallon bucket (by hand) then pour in the mixture. You should see an immediate drop in PH, and it will stabilize it.

Then, as a second and more long term method go an buy some crushed clam shells at the pet store. Crushed coral will work nicely as well but it's slightly more expensive. I put about 1/2 a bag in my filter so as the water passes through them it's constantly washing over the coral. When the PH want's to climb the calcium in the coral leaches out and balances it (instantly).

I have not had a PH swing in over a year. It holds rock steady at 7.5

Here are some interesting articles about baking soda and pond PH.

You should also make sure your nitrates are ok. If the PH crashes it can kill the fish quite quickly.


    Bookmark   May 16, 2012 at 11:03AM
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I have heard the stories about test strips being inaccurate. However I can assure you that test paper from a working lab should be accurate. If the paper has been sitting in someone's 110 degree F. attic, then that's another matter.

If you decide to try baking soda, I see no reason to break the rule about changing pH slowly. That is why I suggested that you just throw the product, still in the box, into the pond so that it will disolve over a matter of days.

    Bookmark   May 16, 2012 at 2:49PM
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Negative on the box idea. Dump it in, baking soda won't drive the Ph 'down' into dangerous territory. It just acts as a buffer to help eliminate the dangerous swings.


Also, Ph is just one leg of this 3 legged stool. What is the Ammonia levels? What are the Nitrate levels? High Ph with high ammonia equals dead fish, quickly.

Thats why it's important to get carbonates in the water (crushed clam shell/coral). It helps smooth out the Ph swings.

But the OP also needs to make sure his other levels are acceptable.

Water changes will help with that.

    Bookmark   May 16, 2012 at 3:14PM
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buyorsell888(Zone 8 Portland OR)

The pond store clerk who told you the green/pea soup algae was caused by high ph is either a liar or clueless.

High ph does not cause algae.

Many ponds go through a green cycle in spring when their filters and plants are taken out for winter and they are cleaned and started up again. It is the same with new ponds.

Dumping all these chemicals into your pond is a lot worse for your fish than a little green water and high ph....

    Bookmark   May 16, 2012 at 6:06PM
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"Negative on the box idea. Dump it in, baking soda won't drive the Ph 'down' into dangerous territory. It just acts as a buffer to help eliminate the dangerous swings."

Why so Negative, groundbeef? We only need to go to the last sentence above to see that you might agree with me. And if necessary we can go down a couple of paragraphs to:
"Thats why it's important to get carbonates in the water (crushed clam shell/coral). It helps smooth out the Ph swings."

I expect that we can find other reasonable statements from you stating that rapid changes are bad or at least best to be avoided. All I suggested is that it would be better to prevent one rapid swing. I did not say that rapid bicarbonate introduction would swing pH into dangerous territory. In fact, my (and the first) initial response to the OP said:

"Usually, people who have problems just throw a couple boxes of baking soda in the pond. That would bring the pH to ~8.3 from low or high."
At the time, I was attempting to suggest that the introduction method and amount was of no particular concern, rather than refering to a closed box. But it is still a fine idea and in fact is just a faster but similar action to your last suggestion of adding coral etc.

    Bookmark   May 16, 2012 at 8:37PM
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Sorry, wasn't trying to be 'negative' in my response.

Because the OP is having high PH issues, and didn't indicate any of the other readings of his (or her) pond, I would err on the side of lowering the Ph and stabilizing it quickly.

There isn't much downside to rapidly pulling a 9.0+ Ph down to 'good' (7.0-7.5). And the advantage of the baking soda is that you literally cannont drive downt the Ph 'too low' even if you dump 50 boxes in the water.

Thats why I said rather than dropping the whole box in to slowly dissolve, just dump it in and take care of the problem. Then use the crushed coral to take care of the ph swing problem long term.

Have a great day.

    Bookmark   May 17, 2012 at 8:54AM
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Here is about the best article on Ph fluctuations and how baking soda can both raise AND lower Ph to the acceptable range of 7.4-7.8 and then 'buffer' the water to prevent further fluctuations.

I would suggest any ponder print it out and keep it as a reference. It's very good.


    Bookmark   May 17, 2012 at 9:00AM
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That is a good article and I read it because by your post you said that baking soda would lower the ph to a level in the 7's. But that isn't true and the article doesn't say that. Yes it will lower very high ph but never lower than the 8's and if you put too much in it will raise the ph to the 8's. What you don't realize is that most well water in the midwest is from limestone wells which is mostly calcium carbonates. Adding baking soda won't do anything as the water has all carbonates that it can dissolve. The only way to safely lower the ph is to remove some carbonates in a controlled way. There are two ways to do this. One is to add enough acid to lower the level of carbonates and the ph will come down. This is very difficult to do manually. If you are going to do this on a pond you need to use computer controlled metering equipment to adjust the ph. The other way is to use a dealkalizer that is like a water softener. This will remove most of the carbonates in the water being put in the pond. But normally the pond will be better off if nothing is done.

    Bookmark   May 18, 2012 at 9:57AM
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I think we are all in agreement that ste1957 should not worry about his(?) hard water and lowering pH will not help the green water. We are also in agreement that baking soda is usually a good thing to add to the pond unless you already have very hard water in which case it is not necessary.

    Bookmark   May 18, 2012 at 11:53AM
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@ Mike in IL

I live in Springfield IL, so I'm well aware of the water quality.

And my pond was doing quite swimmingly for 4 years, until last year. When the carbonates in the water were eventually exhausted. I use a rubber liner, not cement.

Eventually the pond due to the nature of the cycle will use up all the carbonates (unless you have a cement pond).

Thats why the baking soda is a good 'band aid' when the Ph begins going nuts (as in my case). Long term though you need calcium carbonates in the form of crushed coral or clam shells.

You are correct though, it won't drive down the PH much past 8.2. But it will drive it down if it's above 8.2.

It can do both. Either raise the PH if it's crashing or lower it if too high.

Hence it's usefulness as a buffer.

    Bookmark   May 18, 2012 at 11:54AM
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Hi Groundbeef,

I am sorry to hear that you also live in IL. You as I have the mistake of living in one of the worse states in the country.(LOL)If you get your water from the city of Springfield than chances are that you don't have well water. Most if not all the water in Springfield comes from lake Springfield. Most of the water in the lake comes from surface water and doesn't have the carbonates that most of the well water in IL. I live in a city that gets all of the water from shallow and deep wells. This water has alkalinity of 425 ppm and hardness of 430 ppm. So unless you are doing no water changes with the well water the carbonates will never get used up. As others have stated this water will not be a problem for the pond. I do have a dealkalizer and have been able to keep the ph in my pond at 7.5. I have not used it in several years as it was more costly than it was worth.

Yes it can raise or lower the ph depending what the ph is. The article is a very good article as far as it goes. It only talks about part of the chemicals in baking soda. Bake soda is NaHCO3. The HCO3 does get used up but not the Na. Very little of the Na is used up in pond processes. That is why baking soda is a good quick fix but if I was looking for a long term fix I would look at Calcium Carbonate. As the carbonates get used up the Calcium is used by every living thing in the pond. The second thing is if your source water is low in carbonates it is probably low in Calcium also. That is why in the article he talked about using things like coral as a long term fix. Coral is mostly Calcium Carbonate. It is how limestone was made which is mostly Calcium Carbonate. The problem is getting enough in the pond so that it can dissolve fast enough to keep up with the acid that is being produced by the pond.

I want to apology if my comments came off as me attacking you. That was not my intention. My typing skills are poor at best so my comments tend to be short and to the point. This can and does sometimes be offensive. So once again I would like to apology to you.


    Bookmark   May 18, 2012 at 3:17PM
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Just a follow up on my ph levels. I always thought you had to have ph correct before you can correct any water issues. I was wrong! I went out and bought a tetra pond uv18 and it took that pea green soup water to crystal clear water. For the first time in 3 years I can see the bottom of my pond. And for the ph I gave up on it. It is still at 9 but my fish and plants are now finally growing. So farewell to all you pond store retailers on all your chemicals you have sold me over the past 3 years. And also you all my want to lower your prices on uv lights. I saved around 268.00 dollars by going on line and having shipped to my home. Thanks all for your help

    Bookmark   June 8, 2012 at 5:13PM
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FYI. I've kept a block of paster-of-paris in my skimmer next to the pump for 3-4 years and to date have had excellent success with my pond. has the this helped,no clue. I've not checked the water for anything in as many years, but I do keep as many plants as possible in the ponds ( one of about 600G, another about 85G?

I have several Koi, one approx 24" and 12 years old, the others 3-5 years and avbut 15-18" - just reporting, uou can decide.

    Bookmark   June 9, 2012 at 10:27PM
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How does plaster of paris help in the ph level of your pond. I just added a ph reducer and now wish I hadn't after reading these posts. I also have green water problems.

    Bookmark   July 23, 2012 at 2:35PM
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Plaster of paris is Calcium Sulfate and it buffers out around pH 5.6 so it would be expected to drive pH levels down toward that pH assuming the water was at a higher pH. pH 5.6 is too low for fish. However, since the block isn't going to disolve rapidly, I would imagine it might be useful in a situation where the pH of the water source is above 9. But, as above, sodium bicarbonate will hit the perfect pH of 8.3 and shouldn't ever cause trouble.

    Bookmark   July 23, 2012 at 11:22PM
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RE the green water - I've heard that benenite (sp) will clear green water. I bought some few years ago, from Gails Koi, Guthrei, OK, 405-396-8000. I only had slightly green water and used it a few times, and I also keep a block of plaster of paris in the skimmer box, and my water is clear so I'm not sure if the benenite really helped. It wasn't expensive so maybe worth consideration - FYI

    Bookmark   July 24, 2012 at 6:59AM
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