Algae on my waterfall stones

catherinet(5 IN)May 4, 2009

I finally built my little waterfall this year. My 300 gallon stocktank doesn't have any algae in it, but now algae is completely covering the main rock on the waterfall, right before it goes into the stocktank.

Why is that? Do I just scrub it off if it gets too thick?


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If your waterfall is in the sun, then you will get algae. You can either scrub it off or what I do is on a weekly basis pour some Hydrogen Peroxide on your waterfall. You can get bottles very cheap at the local drug store. The Hydrogen Peroxide will kill the algae but you must stay on top of it. I use a quart in my 1800 gallon pond. The Hydrogen Peroxide will add extra oxygen to the pond as well which will help the fish on very hot sunny days.


    Bookmark   May 4, 2009 at 12:24PM
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I pull it off mine & toss it in the yard, LOL. But some always falls off into the pond, which I don't like ... I don't have a bottom drain. So last time I shop vac'ed it off, LOL. Needs it again already.

    Bookmark   May 4, 2009 at 3:51PM
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catherinet(5 IN)

Its almost like having carpeting on the stones, and the sound is muted. Plus, the water seems to slide, inside of flowing.

    Bookmark   May 4, 2009 at 7:32PM
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ron_a_nj(Z6 NJ)

I usually rake it off and fling it on the lawn. This year, it all died off on its own in a week after I turned on the UV.

    Bookmark   May 5, 2009 at 8:55AM
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catherinet(5 IN)

Its not the stuff I can pull off. I'll take a brush to it later today and see if that works. Maybe I shouldn't fight it and just see what evolves.

    Bookmark   May 5, 2009 at 9:17AM
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Shut your pump down. Put some peroxide in a spray bottle. Spray liberally, wait a few minutes then turn your pump back on. Algea dead and gone.

If there is alot I would clean it off so it doesnt clog your pump. Stiff bristle brush will mowrk just fine. But still use the peroxide. The 3% stuff you can get at he drug store a qt is less then a dollar.

    Bookmark   May 5, 2009 at 9:37AM
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I'm having some algea at the waterfall also. 2 days ago I did the Hydrogen Peroxide thing and didn't notice any difference, yesterday I did some AlgeaFix, still didn't notice much improvement. This evening I will try billnpa's suggestion of turning off the pump and spraying with the HP.

    Bookmark   May 5, 2009 at 10:06AM
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catherinet(5 IN)

I'm wondering why it likes it there so much. Any ideas?

    Bookmark   May 6, 2009 at 5:33PM
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catherinet, I asked my local water garden nursery about the algae in my pond. They just said the sun grows plants. And it would go away once my garden plants started growing.

He also said to use either bleach OR hydrogen peroxide and that would also take care of the problem. My waterfall and rocks have plants growing around them and over them so maybe that would help you.

    Bookmark   May 7, 2009 at 7:05PM
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I would advise against using bleach in your pond. Bleach is sodium hypochlorite and will leave a variety of residuals (hypochlorous acid, hypochloride ions, chloramines as well as a few chlorinated organics) in your pond that are toxic to fish and other plants. Using hydrogen peroxide sprayed or sloshed on you rocks when the waterfalls is turned off will work without any toxic after-effects. Turning the water off for a brief period (15-30 minutes) is important otherwise the running water will rinse the hydrogen peroxide off the surfaces you are trying to treat before any reaction can occur. But don't leave the water off too long or your biofilter will run out of oxygen and do a number on the nitrifiers in there. The attached algae will grow on the rocks in the streaming water because the water moves the most amount of nutrients past the algae compared to what occurs just sitting off to the side of the pond.

    Bookmark   May 7, 2009 at 9:49PM
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horton(6 b Ontario.)

Where have I seen those initials [DRH] before? LOL
Welcome back Prof!
Hope you intend to stay around.

    Bookmark   May 8, 2009 at 7:50AM
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catherinet(5 IN)

Thanks everyone,
don't worry.......I'd never use bleach. I'm even a little nervous to use peroxide.
That's interesting....about the increased nutrients feeding the algae on the waterfall rocks. Thanks for that explanation David.

    Bookmark   May 8, 2009 at 8:08AM
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One additional comment: some folks have swimming pools and use the Bacquacil system. As part of that system you periodically use hydrogen peroxide (if I recall correctly!)..while you can use this instead of the stuff you buy in the grocery store BE's usually a much stronger solution 10-12% so you'd use a lot less. It will do the same thing, however.
P.S. Hey Horton! Just out and about for bit. Pretty soon the planting begins...assuming you quit sending us rain every day!

    Bookmark   May 9, 2009 at 12:06PM
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catherinet(5 IN)

I feel sort of stupid. I was out there watering some lilies I had just planted around the top of the stocktank watergarden, and decided to spray the waterfall rocks.......and the algae came right off!

    Bookmark   May 11, 2009 at 12:38PM
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sleeplessinftwayne(z4-5 IND)

David, I didn't catch this thread right away but I am glad to see you posting again. You have been missed as much as your advice and I hope you stick around for a while. Sandy

    Bookmark   May 11, 2009 at 1:42PM
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Hey Sandy, you know me! Old, forgetful; website? post? Huh? But I'm glad you and Horton are holding down the fort!

    Bookmark   May 11, 2009 at 9:42PM
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ademink(z5a-5b Indianapolis)

Hi Catherine. :) Yes, you can spray it off. I actually leave it. It's good for a coat of algae to get on stuff - it's like a normal pond and if you get obsessed w/ having something that looks more like a clear, clean swimming'll start to hate your pond. lol

You will also get string algae - now that's fun stuff. Most people go ballistic trying to fight it but I've found if I leave the string algae, it is a MAJOR filtration warrior. It sucks mega nutrients out of the water and all of my suspended algae goes down to zero. It eventually starts to die and I pull it out w/ a cheapo, new toilet bowl brush.

Just like eatin' spaghetti. ;D


PS I throw it all over the yard LOL

    Bookmark   May 12, 2009 at 12:15AM
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ronaye(7? NW WA)

Holy crow, I haven't been here for years and look who I see! How the heck are you?? How's that beautiful Vermont Pond?

    Bookmark   May 15, 2009 at 9:36PM
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catherinet(5 IN)

Thanks Andrea,
I didn't mind the looks of it, but it almost completely silenced the sound of the water on the falls! It was like having all the rock carpeted.
Its funny, but I haven't had any string algae since my whiskey half-barrel pond many years ago.
I do have lots of floating algae in my above-ground stocktanks, but as soon as the lotus and lilies start growing, it all seems to disappear.
The toilet bowl brush is a good idea for that string algae!
So you're saying you eat your string algae, just like spaghetti? ;)

    Bookmark   May 15, 2009 at 10:08PM
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Hey yourself, Ronaye! No sting algae (just to keep the thread "official")! Haven't even had to break out the toilet bowl brush!

I haven't been out on the boards until just recently myself...been busy for few years/months, etc.

    Bookmark   May 16, 2009 at 8:57AM
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sleeplessinftwayne(z4-5 IND)

I think I have died and gone to heaven. Horton, David and Ronaye back together again.
Ronaye, I got here just about the time you vanished but your name on the FAQs and mentions of you have kept you a part of the forum. Thanks for the pond education. You and David and Horton have been great teachers. Sandy

    Bookmark   May 16, 2009 at 4:17PM
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sleeplessinftwayne(z4-5 IND)

Oops. Sorry about the hijack Catherine. Glad the algae problem is solved. Sandy

    Bookmark   May 16, 2009 at 11:57PM
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catherinet(5 IN)

That's okay Sandy! I'm glad everyone found each other again!

    Bookmark   May 17, 2009 at 9:14AM
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Interesting comments. Thanks. I have a (I think) related situation. Not string or floating algae, but all my stream pathway and waterfall rocks are coated with what I'm guessing to be an algae. Or is it? My water is clear, but the stones are darkly discolored. I'm reluctant to use chemicals as I have a number of plants in the water feature, and the birds like to bath and drink in the small pools. BTW, I empty the main and small ponds and do a thorough cleaning each spring. Maybe that's the time for the H2O2 treatment. Any suggestions? Or comments?

    Bookmark   July 20, 2009 at 5:53PM
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catherinet(5 IN)

I just hate putting anything unnatural into the water. So I guess I'm compromising. I just have a small waterfall, so it might be worse for you if yours is alot bigger.
I bought a long-handled grill brush and scrubbed the rocks. it helped a little, but I think the algae is probably going to grow back quickly, just because the rocks are constantly bathed with the nutrients in the water.
My rocks are very dark and not very attractive with that algae on them.

    Bookmark   July 20, 2009 at 6:40PM
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mantorvillain(z4bMN Dodge)

My lowest flat stone at the 'foot' of my waterfall seems to 'cycle' with periods of being covered with green algae then it almost seems to wash away and eventually start up again.

    Bookmark   July 20, 2009 at 9:16PM
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Resurrecting a way old string on the topic of string algae... oops, no pun intended! :-)

Read about Barley Straw bales floating to prevent algae in ponds and am wondering if this would be a solution for our pondless water fountain. We have had a major case of string algae this year and last. Have just tried the hydrogen peroxide treatment (too early to see if it has fixed it) but it seems like floating a barley bale in the water reservoir well of the fountain might work? Anyone try this on a waterfall/water fountain installation instead of a still pond? Thanks in advance for the help!

    Bookmark   August 10, 2014 at 12:50PM
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waterbug_guy(Phoenix AZ (Melrose))

History of the barley myth.

Hydrogen peroxide kills algae on contact and the string algae turns white or lighter color. It's an oxidizer like bleach. It doesn't remain in the pond very long, minutes. So if you didn't see any change when first applied that's about it. It takes a lot of hydrogen peroxide to effect algae. There are high concentration hydrogen peroxide products specifically for algae.

    Bookmark   August 10, 2014 at 4:36PM
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Is this algae on the rocks or moss? Do you have photo?
Just my opinion but I like moss.

    Bookmark   August 11, 2014 at 7:35AM
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@waterbug_guy: thanks, didn't realize barley was a myth! if it seems too good to be true, it probably is...right!?!?

@LJS8510: Love my moss, too! I wish it were all moss...this is definitely the string/spaghetti algae :-(

I appreciate the replies.....too early to see if the hydrogen peroxide keeps it from coming back. We hand pulled out the big blobs, and poured in the peroxide after.

    Bookmark   August 11, 2014 at 7:54PM
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waterbug_guy(Phoenix AZ (Melrose))

@waterbug_guy: thanks, didn't realize barley was a myth! if it seems too good to be true, it probably is...right!?!?
Probably. But really if think everything anyone ever says about ponds is a myth you're going to be right almost all of the time.

Here's my experience with hydrogen peroxide. I didn't learn much, algae is tricky. It can kill at least some species of string algae but that isn't generally too helpful because it comes right back. So to actually control it takes a lot of hydrogen peroxide.

The problem with understanding algae is when one species seems to go away another appears. Then you're left wondering if what you're doing is responsible or did killing it once just make room for another species which is actually responsible for the disappearance of the other species. Trying to come up with experiments to figure it out is frustrating. Complicated little world they have.

    Bookmark   August 12, 2014 at 7:46AM
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There is a product called Pond Balance that works well
I am unaware of any downsides of this product, except cost. But I'm sure like most there are some, maybe someone else could speak to that?

    Bookmark   August 12, 2014 at 9:39AM
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waterbug_guy(Phoenix AZ (Melrose))

Interpet Pond Balance aka Blagdon Blanket Weed Buster aka Interpet Pond Balance.

There's no way way to tell if there are any downsides to the product because the company doesn't say what's in the product, even on the MSDS which makes me very suspicious. The MSDS is the one place where companies are required to disclose dangers. A product that kills algae and stops it from growing imo should be disclosed in MSDS because it kills stuff. Killing stuff is fine as long as it's used properly and the way we know how to use it is the MSDS. The one thing their MSDS does say is the product should not be allowed to enter any water way. But they don't explain why.

Sellers say this product works many different ways, many say it removes a key nutrient, some say plural nutrients. Some say it has bacteria that kills the algae. Some say bacteria is in there to remove sludge (they call it Sludge Buster).

Lets take the easy one first...bacteria. These types of products imo are virtually all scams. They work if you want to believe they work.

The more interesting claim is the nutrient claim. It's interesting to me because this type of thing has been well tested and document for a long time in lake management. The nutrient I'm thinking of is phosphorus.

There are several chemicals that will make phosphorus unavailable to plants and given the directions for Pond Balance and expected results I'm guessing the chemical they're selling is alum (aluminum sulfate).

Alum effect on fish has been tested in several studies and seems to have no effect on fish. In low pH water there was some risk in theory but in practice no harm to fish has been seen.

Backyard ponds can have more extremes than lakes so pH risk could be higher. Alum could drive pH down, but I'm not sure what the risk is. If used in a pond with very low KH the risk to fish might be high, depends on the health of fish. Many times fish will go thru a pH crash with no obvious signs, owner doesn't even know anything happened. But if fish are already stressed a pH crash can be a tipping point. In lake management water is often pH buffered first if needed.

Whether alum works in a person's pond depends on a few things, like pH, your water source, how clean you keep the pond bottom and plants in the pond (soil/fertilizer). In lakes when alum is effective in algae control the results lasts for more than 5 years. In backyard ponds that kind of long term control is less likely because of pond cleaning and water sources, but can still be effective for a long time.

However, Pond Balance MSDS says the product is a pink color and alum is white. But they could just color it or mix in some other stuff.

Why doesn't Interpet disclose what's in the product? Well, if it is alum they sure don't want you to find out because their product is 6 to 30 times more expensive than alum (aluminum sulfate) which you can buy in any decent garden supply.

That's very typical for many pond products. Take a proven chemical used in waste water treatment and/or lake management and box it up, add some color or "bacteria" and sell it like it's something they invented and hide what the product actually contains. They have to do zero research or testing because it's already been done.

Anytime you can resell something for 6-30X mark up you're doing good.

Is that a scam? That's a personal opinion.

IMO, it isn't a scam if it is alum, it's capitalism. It has at least the potential of doing at least one of its claims. Where they get into scam territory imo is claiming it's perfectly safe. Nothing is perfectly safe. If it's alum I'd say it's safe for 99.9% of ponds. The unlucky 0.1% aren't going to make enough noise to hurt sales. I'd prefer companies be more clear about what is in a product and in what cases, even if extreme, the product becomes dangerous.

Perhaps someone who uses Pond Balance/Blanket Weed Buster could confirm if it's alum.

    Bookmark   August 12, 2014 at 12:31PM
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I did do research trying to find out what is in PondBalance because like many I also was very much against putting anything in the pond, especially if I don't know what it is.
But never found anything conclusive. We had string algea problems in our first smaller pond but just did the work of removing it for several years.
But when we replaced the smaller pond with a larger one 5800 gallons, it became impossible for us to keep clear. My wife heard of Pond Balance & tried it.
For us it has worked extremely well since 2005.
Yes it is expensive, but well worth it, we never have string algae anymore, but I would still like to know whats in it.
We did have a problem this spring with young fish die off but I don't think its related but do not know.

This post was edited by LJS8510 on Sat, Aug 16, 14 at 7:29

    Bookmark   August 15, 2014 at 12:52PM
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