When did you test? Morning or evening? Green water will cause dramatic swings in Ph from the morning to the evening. This change in pH is worse than the high pH. Please do NOT add any pH down product. What you need to do is STABALIZE the pH, not chase it every day adding different products.

Please test your kH. A high pH is not a problem so long as you also have a high kH. The kH is your alkalinity and it acts as a buffer for the pH. The kH is what stabalizes the pH. In fact it hardly matters at all what the pH is, so long and the kH is high.

So do two things, start testing your pH twice a day to monitor the daily swing and start testing for kH. You want the kH to be above 80 ppm, above 100 is better. And if you have a bead filter, get it above 150. If it is too low, add Baking Soda (sodium bicarbonate). Just regular old Arm and Hammer will work. Add one pound per 1000 gallons to increase the kH by 70 ppm.

Also, while you are testing kH, test your tap for kH as well. If you tap has a high kH, then you only need to do a water change to increase the kH of the pond.

Thanks for the info. I'm going to buy the KH test kit tonight. In the meantime, yesterday it rained quite a bit which had lowered the PH (I guess the only good thing about 'acid rain').
Also my husband was able to borrow a PH meter for the night so we were able to take the following readings:
6:30pm 23C PH=9.1
10:20pm 22°C PH=8.8
6:45am 20°C PH=7.9

Seeing these results makes me feel alot better. I forgot that PH can increase during the day and drop overnight. I didn't realize that it would change that much. I usually test in the evening once I'm home from work. I'm still going to test the KH once I get the test kit.

As for the algae and pond scum?... I still constantly cleaning it out. I attached some closeup pics. I don't know what you call the floating algae... or is this just the same algae but starting to get broken down by the beneficial bacteria?

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Net out as much as you can. You can use a toilet brush to twirl it out too. It grabs it.

As your plants grow they will use nutrients that are feeding the algae. Beneficial bacteria aren't going to stop algae from growing or kill it. You've got a lot of water and not very many plants. Do you have submerged plants? They can really help.

Messing with your ph with various chemicals is worse than having a stable high ph.

It should not swing that much, it's the algae that is causing this. Most ponds will swing less then .5 from morning to evening. That daily swing in the pH is a bigger problem then a high pH. Over time this can stress the koi considerably.

Test your kH, if it is low, then hopefully raising it will solve the problem. But if it is high and you still have this swing, you really need to do what you can to remove the algae. Perhaps a UV filter or increasing bio filtration.

jcjcjcx:

I buffer my pond with baking soda. I use a half kilo box about twice a year (for 1100 gallon pond) and check KH with a kit to make sure it is in recommended concentration. This stops radical pH swings caused by acid rain or day night swings. Read the article I refer to.

I get similar string algae to yours. I use a fine mesh net to scoop it out. Once my plants start growing vigorously, the string algae slows down. It never goes away completely.

So I bought the KH liquid test (by API) and tested my pond water and the tap water last night (around 9:30pm). Here are the results:

pond:
6 drops (6 °dKH) = 107.4 ppm KH/GH
tap water:
5 drops (5 °dKH) = 89.5 ppm KH/GH

So I think my KH level is okay? Of all the tests, this one is new to me and I'm having trouble understanding it (did the test properly, but just don't understand the results and what to look for). Thanks for the link, Kalevi. I'll read over again, it lost me there.
Anyone.. feel free to explain it in layman terms...
Thanks.

seems like your alkalinity is ok. Strange that it is higher in the pond then in the tap but you are still ok.

Alkalinity if basically the buffer for the pH and it helps to stabalize the pH. With that much algae keep testing kH weekly. if it gets too low (below 80) then add baking soda. With all that algae a low kH can cause problems.

For now do the best you can to remove the algae. A UV would be a good place to start for green water. Also, Koi Clay can work wonders on the string algae. When I have string algae I will usually add a cup per 1000 gallons.

Thanks for the tips! I'll try Koi Clay and monitor the PH and KH.
Looks like the fish weren't too bothered by the high PH and murkiness of the water, because I just noticed that there were some eggs laid in some of the algae, and saw at least a dozen small fry swimming near it. Wow, can't believe they started already.

I am bumping this thread up for the benefit of a current questioner.

I have a printed message from Kalevi from 6/05 which describes the use of baking soda and plaster of paris for maintaining proper water hardeness and PH. I have been using the POP pills for two years with wonderful results--NO ALGAE, no need for a UV light. Thanks, Kalevi!

An update on my pond...

I guess now my pond is going through an algae bloom. I said before that the water wasn't really pea soup green.. well now it definetely is. The water is so green and murky, I can't even see if there is any string alage in the pond. I put in a koi kastle last winter which I haven't seen for weeks .. and its sitting only at 2 feet deep. I'll reach in with the net and get some string algae.. but I can't see whats down there at all. I've never seen my pond this green and unclear.
I'm starting to get more impatient. I went to our local pond shop that recommended that I use Interpret Pond Balance. Put first dose in last week, but it made no difference so far. Probably just wasted $76. Maybe I should have tried the Eco-Floc instead. Don't want to waste more money, plus I don't like the idea of putting chemicals into the pond.
Interesting read on the thread about hornwort. This is the first year I thought I'd try something other than hornwort so I bought anarchis and cambomba instead, and now here I have all this green water.

When my water was GREEN this spring, the things that conspired to clean/clear my water for me were: UV light filter, floating barley bales (although they take three weeks to begin to work), LOTS of anachris and aquatic plants and, most importantly, patience. I think I've read somewhere that hydrogen peroxide will safely kill the string algae. Adding koi clay will also clarify your water. These are all safe, natural ways to balance your pond. Chemicals will only provide a temporary fix.

Hi; I just found this site and have learned so much from your postings about merky water and high PH. I have a farm pond about 1/4 acres. It looks just like the above photos but also has duckweed and watermeal. Would sodium bicarbonate also help this? Thanks for any information. Also how much bicarbonate would I use. I think the pond is 12 feet deep. Thanks again. C.

I apologize for the length of this post in advance. As has been mentioned above your high pH is most likely the result of the algae bloom that you are experiencing. Typically -again, as inferred above - algae consume carbon dioxide during the day causing the pH to increase and produce carbon dioxide (along with the bacteria and other things in your pond) during the night lowering the pH in some cases as much as 1.5 pH units (a factor of over 30x the hydrogen ion concentration!). Where I live we have to shut down the biofilters during the winter and essentially start the pond and filter up each spring. When this begins I will typically get a bit of suspended algae then a fair amount of stringy, slimy algae. Yet when I turn on the pumps (I usually wait until the water temp is above 45 or so since the biofilter and associated nitrifiers wont do much of anything below that temperature) the floating, stringy algae as well as the suspended algae are essentially gone within 72 hours. Even the algae on many of the rocks is either absent or drastically reduced. I try to use and do things that fall under the category of "do no harm". I have barley straw in the waterfall housing - not that I particularly believe that barley straw works just that at moderate application rates it doesnt appear to harm anything.
Click here for article about barley straw
I add salt to get the salinity level (not the same as measuring the sodium concentration) up to about 0.05%-0.1%. I do this because there are some non-scientific reports indicating that salt will suppress string algae growth. More importantly I do this to increase slime coat production of the fish until their immune systems can catch up with the other "bugs" in the pond - typically above about 55 degrees or so. If necessary I will add hydrogen peroxide to the tune of 1-2 pints per 1000 gallons (some folks add hydrogen peroxide at the rate of 1-2 pints per 100 gallons - using 3% store stuff). Both salt and hydrogen peroxide are, again, fairly benign in that all of the plants, frogs, toads, fish, etc. tolerate relatively wide variations in dose regardless of temperature and other factors. So if you dont know the exact pond volume or you happen to spill a bit too much...not a problem. Again, this fits in with "do no harm".
Click here for Excel spreadsheet to calculate hydrogen peroxide doses -see bottom tab on spreadsheet
In addition to all of this I will sometimes add daphnia once the water temperature hits 65 or above. These are highly efficient algae eating bugs, fish eat them, some fish fanciers actually grow them to feed them to their fish. The following is a web article, non-scientific publication on daphnia for algae control.
Click here for web article on use of daphnia for algae control
The other thing I do is add sodium bicarbonate to provide alkalinity and protect the pond from the potential of a pH crash. And it is at this point I wanted to clarify what alkalinity is and is not doing for you. You may just wish to skip what follows. If not, then you may want to open the jpeg graph/image in another window. If, after this, you wish more information please drop me an e-mail and I can explain the chemistry in much more detail or alternatively send me your phone number (if you are in North America!) and Im willing to call and chat with you, if you would like. Please dont ask me to call you just so you can give me a hard time I have others who are willing to do that for you! :-))

Alkalinity in our ponds is predominately the result of the bicarbonate ion. There are many other potential buffering systems out there but this is the only one of any significance in a natural system. The red line in the diagram represents what happens as you add your KH solution to your vial you start at some beginning pH (in this diagram Ive started at ~8.3 where the blue line passes through the red line) and as you add drop by drop the pH in the vial changes until you get a color change. This occurs at a pH of approximately 4.5. You calculate your alkalinity by counting the drops and then multiplying by 17.9 (the conversion factor to convert to ppm). Essentially what you have done is measured the amount of acid added to the vial - the horizontal distance from the vertical, blue line to where the pH changes to 4.5. So what? Notice that there are regions in the curve, where if you could record the actual pH as you added the drops, that the pH doesnt change too much - indicated by those ovals around pH 6.3 and 10.3. These are the points of maximum buffering intensity. Also notice that the pH drops fairly dramatically in the pH ranges of 8.3 (very important!) as well as around 4.5. These steep, vertical regions are ranges where there is minimal buffering of pH swings. In the pond described above the pH is as high as 9.5 (just visually move the blue line to the left a bit). When you add sodium bicarbonate it will not drop the pH much, but more importantly it cannot protect your pond very well from pH swings in the pH 7.7 to 8.7 region. Adding sodium bicarbonate will move the whole red line to the right (adds alkalinity) but you will still have this same region permitting pH swings to occur. Please do not think that I am saying not to add sodium bicarb (good, old Arm & Hammer). But to really control the pH swings you need to go after the algae. You need alkalinity in your pond to eliminate or protect against a pH crash.

Again I apologize for this long post. Hope it is of some help.
David

Hi, JCJCJCX. If you still haven't been able to clean up your pond, I can help you and you will never again have green water or hair algae. Filtration is the answer and you can make your own in no time, save yourself time and money. If your interested, let me know. I am also in Zone 5, hopefully we're not too far apart.

Yours Koily, Lorraine

Great information...

My pond did eventually clear in the summer, but it did take a long time compared to previous years.

This year... well right now I'm in the middle of rebuilding my pond, so I don't have to worry about green water at this point. (Having other problems).