Algae problem


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I have a relatively small pond (about 250 gallons) with a large waterfall (about 10 ft wide and about 5 ft high). I have had this pond and waterfall for 18 years and, until about a year and a half ago, had no problem with algae using only a 3 inch chlorine tablet always in the water. But, about a year and a half ago, I suddenly developed a big algae problem. My landscaper suggested that I remove the river rocks at the bottom of the pond so that debris and algae could not "hide" under these stones. He also suggested that I add an algaecide and a phosphate chelator. I did all three but to no avail. The algae keeps rapidly returning (1-2 months). I drain the pond, partially refill spraying the sides with a hose, and repeat until I have crystal clear water. And, then, of course, continue to add the chlorine tablet, algaecide and phosphate chelator. But, the algae always continues to come back within a month or two. I am a retired Professor of Microbiology and my background suggests to me that I have selected a strain of algae that is resistant to all these control methods and, thus, the algae comes back to noticeable levels in a month or two (depending on the temps). I live in the desert in Arizona where we get a lot of blowing dust which settles in the pond which I suspect helps the algae. But, as I said, in 18 years, I never had this severe problem before . A friend suggested that I "shock" it. What is "shock"? And, what will "shock" do to the wildlife that drink out of the pools of water on the waterfall. We love watching all the wildlife drink from these pools of water which include rabbits (as many as 3-4 at a time), huge numbers of quail, huge numbers of doves, many, many other species of birds and also ground squirrels, chipmunks, etc. I do not want to do anything to the water that will kill these wildlife. CAN ANYONE OFFER A SUGGESTION ABOUT HOW TO CONTROL THIS ALGAE PROBLEM WHICH HAS OCCURRED ONLY AFTER 17 YEARS WITH THIS POND WITHOUT HARMING THE WILDLIFE WHICH DRINK FROM THE WATERFALL OR THE LARGE AMOUNT OF ORNAMENTAL PLANTS SURROUNDING THE POND WHEN I DRAIN IT ABOUND THEM? Thank you, Bruce
 
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Shock is a very strong dose of pool chemicals, not good for wildlife to drink. May I suggest adding plants to outcompete the algae for nutrients. It takes longer, but will eventually get the job done with enough plants. If your pond is in full to partial sun, try adding a few small growers, there are “ dwarf” water lilies which are good for shallow areas, but may tantalize deer and raccoons to munch. Other options include water lettuce, water hyacinth, mosaic plant, which will cover the surface and thus reduce the algae’s ability to photosynthesis
 
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It is extremely interesting that this problem has developed after all these years. I think you landed on the reason though - something has found you that has managed to defeat humans... this is how the world will end! haha! Is this string algae on the rocks? Green algae in the water? Combination of both?

Like @JamieB suggested, I would add plants to the equation if you don't already have them. Let nature do her thing. The other thing missing from the system is fish - could you add a few goldfish to your pond? The fish will feed the plants, the plants will eat the excess nutrients in the pond and everyone will be happy!

But in addition to that, I'd suggest two things - the first is sodium percarbonate. This is a powder that kills single celled algae on contact and is harmless to wildlife. I've used it in my pond full of fish for years. When it comes in contact with water it breaks down into hydrogen peroxide and soda ash. It's sold commercially by pond companies under various labels, but it's all the same thing. Shut off the water, remove as much algae as you can by hand (especially if it's thick, string algae) apply the powder while the rocks are still wet, wait 20-30 minutes and restart the water flow. The algae will be gone in 24 hours. If it's a lot of algae, you may need a second application, but it works great. I suggest you look for the product NOT packaged as a pond product as you will pay 10X more if it's sold for ponds. I buy mine from a soap making supplier.

I should add that you could just try straight up hydrogen peroxide - it's cheap, safe, and easy to get. Turn off the waterfall, get yourself a few quart bottles of the plain old drug store variety H2O2, dump it all over the algae, give it time to work and then turn the whole thing back on. You can't use too much - it's very mild stuff. If that works, you could move on to the sodium percarbonate for the future.

My second suggestion would be to simply shut the whole thing down on a nice, hot, sunny day and let the sun bake it until it's dead. This may take more time, but any algae that depends on water to survive will die when the water is removed from the equation.

We would love love love to see your pond! Post some photos when you get a chance!
 

Mmathis

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Hello and wecome!

I’m curious how a 250 gallon pond can have a 10’ wide x 5’ tall waterfall!
 
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I'm thinking you must not be adding a very large dose of chlorine tablets if the wildlife is drinking the water. So the amount you are adding is not enough to kill off the algae. Your friend wants you to shock it. Swimming pool shock is a grandular very high concentrated chlorine. I'm guessing you dont want to do that since everyone is drinking the water.

Is there a way you can put a net or something over the whole thing and then add the shock? The shock will dissipate after a couple days, but will probably kill off the algae. If you go that route, I suggest you get a good chlorine test kit to monitor when you can remove the net.

The thing is, the algae may just come back, so you need a more long term solution. Adding plants was a great suggestion. Add lots and lots of plants. They will starve out the algae by feeding on all the excess nutrients.

Blocking the direct sun will also help since algae is a plant. You can use plants that cover the water surface which will block the sun. Lilly pads, water lettuce, water hyacinths will all do that. The lettuce and hyacinth will also help compete with the algae by taking in the excess nutrients which is what the algae is feeding on. The lillies won't help much with the excess nutrients, but they can help to block the sun.
 
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Shock is a very strong dose of pool chemicals, not good for wildlife to drink. May I suggest adding plants to outcompete the algae for nutrients. It takes longer, but will eventually get the job done with enough plants. If your pond is in full to partial sun, try adding a few small growers, there are “ dwarf” water lilies which are good for shallow areas, but may tantalize deer and raccoons to munch. Other options include water lettuce, water hyacinth, mosaic plant, which will cover the surface and thus reduce the algae’s ability to photosynthesis
Thank you for your reply. My pond is in full Arizona desert sun for most of the day from sun rise to about 4-5 PM. I really do not want to add any plants to the small pond which is concrete. But I do have a number of Yerba mansa plants growing all around the pond which send out tentacles and many of these tentacles have extended into the water with flowers growing.
 
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The other non plant options would be a sun shade or dye, again the purpose being reducing the algae’s ability to photosynthesis. Reduce the light, add peroxide, or other natural product, ( I’ve heard barley straw works, but it takes time to break down and the “extratcs” may be useless)
 
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Rather than poisoning the water why not look at what has changed? You must have something new introducing a high amount of nutrients into the water. I am willing to bet it's more or larger wildlife visitors. This might seem gross, but it is not uncommon for wildlife to 'relieve themselves' in water they drink or bathe in. Do you have a wildlife camera? Might be interesting to see what stops by in the evening. Our neighbor had a mother and two cub bears dropping by for late-night dipping in their swimming pool.
 
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It is extremely interesting that this problem has developed after all these years. I think you landed on the reason though - something has found you that has managed to defeat humans... this is how the world will end! haha! Is this string algae on the rocks? Green algae in the water? Combination of both?

Like @JamieB suggested, I would add plants to the equation if you don't already have them. Let nature do her thing. The other thing missing from the system is fish - could you add a few goldfish to your pond? The fish will feed the plants, the plants will eat the excess nutrients in the pond and everyone will be happy!

But in addition to that, I'd suggest two things - the first is sodium percarbonate. This is a powder that kills single celled algae on contact and is harmless to wildlife. I've used it in my pond full of fish for years. When it comes in contact with water it breaks down into hydrogen peroxide and soda ash. It's sold commercially by pond companies under various labels, but it's all the same thing. Shut off the water, remove as much algae as you can by hand (especially if it's thick, string algae) apply the powder while the rocks are still wet, wait 20-30 minutes and restart the water flow. The algae will be gone in 24 hours. If it's a lot of algae, you may need a second application, but it works great. I suggest you look for the product NOT packaged as a pond product as you will pay 10X more if it's sold for ponds. I buy mine from a soap making supplier.

I should add that you could just try straight up hydrogen peroxide - it's cheap, safe, and easy to get. Turn off the waterfall, get yourself a few quart bottles of the plain old drug store variety H2O2, dump it all over the algae, give it time to work and then turn the whole thing back on. You can't use too much - it's very mild stuff. If that works, you could move on to the sodium percarbonate for the future.

My second suggestion would be to simply shut the whole thing down on a nice, hot, sunny day and let the sun bake it until it's dead. This may take more time, but any algae that depends on water to survive will die when the water is removed from the equation.

We would love love love to see your pond! Post some photos when you get a chance!
Thank you for your reply! Please see my recent previous reply to another suggestion about adding plants. I cannot add fish since there is no rock overhang under which the fish could shelter from the sun. As a mentioned in my reply to the previous suggestion, this pond is in full sun light for most of the day and, here in Arizona, the temps during the summer are very high. This summer we had 48 days over 110. Without shade, fish could not survive.

If I understand your suggestion about the sodium percarbonate, this is a powder which I must manually apply the powder. Unfortunately, I am 78 years old with several physical problems which makes it impossible for me to get into the pond to apply such a powder. In fact, it is getting more and more difficult for me to even drain the pond with a small sump pump, constantly stirring up the sand and algae sludge (no string algae) with a long handle, large industrial type broom (brush), suck up the residual water with a shop vac, then partially refill the pond, drain again constantly sweeping to keep the sludge in suspension, and repeat this 4-5 times before partially refilling until the water is clear and, then, turning on the pump to run the water fall to flush the pipes, then draining again and then refilling.

I have had the waterfall shut down several times for a week at a time while waiting for a pump replacement (why do pumps not last more than a year or so) during which the pond and waterfall had direct, intense sun light for most of the day. But that did not help!

I think I have attached a photo of my small pond and big waterfall by clicking on the "Attach files" tab. I hope that works.
Hello and wecome!

I’m curious how a 250 gallon pond can have a 10’ wide x 5’ tall waterfall!
I have attached a photo of my relatively small pond with the big waterfall hand constructed with huge boulders (not by me but by me.professionals
P0002539Small.jpg
P0002539Small.jpg

Seems like its more of a pump basin at that volumn.
I do not understand your comment. Yes, there is a metal lined well in the bottom of the pond which contains the pump, if that is to what you are referring.
P0002539Small.jpg

I'm thinking you must not be adding a very large dose of chlorine tablets if the wildlife is drinking the water. So the amount you are adding is not enough to kill off the algae. Your friend wants you to shock it. Swimming pool shock is a grandular very high concentrated chlorine. I'm guessing you dont want to do that since everyone is drinking the water.

Is there a way you can put a net or something over the whole thing and then add the shock? The shock will dissipate after a couple days, but will probably kill off the algae. If you go that route, I suggest you get a good chlorine test kit to monitor when you can remove the net.

The thing is, the algae may just come back, so you need a more long term solution. Adding plants was a great suggestion. Add lots and lots of plants. They will starve out the algae by feeding on all the excess nutrients.

Blocking the direct sun will also help since algae is a plant. You can use plants that cover the water surface which will block the sun. Lilly pads, water lettuce, water hyacinths will all do that. The lettuce and hyacinth will also help compete with the algae by taking in the excess nutrients which is what the algae is feeding on. The lillies won't help much with the excess nutrients, but they can help to block the sun.
The three inch diameter chlorine tablet worked great for about 16 years. I really do not want plants in the pond since the pond is so small.
 
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I'm thinking you must not be adding a very large dose of chlorine tablets if the wildlife is drinking the water. So the amount you are adding is not enough to kill off the algae. Your friend wants you to shock it. Swimming pool shock is a grandular very high concentrated chlorine. I'm guessing you dont want to do that since everyone is drinking the water.

Is there a way you can put a net or something over the whole thing and then add the shock? The shock will dissipate after a couple days, but will probably kill off the algae. If you go that route, I suggest you get a good chlorine test kit to monitor when you can remove the net.

The thing is, the algae may just come back, so you need a more long term solution. Adding plants was a great suggestion. Add lots and lots of plants. They will starve out the algae by feeding on all the excess nutrients.

Blocking the direct sun will also help since algae is a plant. You can use plants that cover the water surface which will block the sun. Lilly pads, water lettuce, water hyacinths will all do that. The lettuce and hyacinth will also help compete with the algae by taking in the excess nutrients which is what the algae is feeding on. The lillies won't help much with the excess nutrients, but they can help to block the sun.
Actually, the right end of the pond which gets the most shade is the worst place in terms of algae growth.
 
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Rather than poisoning the water why not look at what has changed? You must have something new introducing a high amount of nutrients into the water. I am willing to bet it's more or larger wildlife visitors. This might seem gross, but it is not uncommon for wildlife to 'relieve themselves' in water they drink or bathe in. Do you have a wildlife camera? Might be interesting to see what stops by in the evening. Our neighbor had a mother and two cub bears dropping by for late-night dipping in their swimming pool.
No, I do not have a wildlife camera. But, the entire back yard is surrounded by 8 ft high walls on two sides and a 6 ft high metal view fence in the back which provides marvelous views of the Superstition Mountains. Thus, generally, only small critters like rabbits, ground squirrels, chipmunks and of course birds can get into the backyard. Possibly, the occasional bobcat but only occasionally. We do have giant desert toads almost every night in the pond during the summer but this is nothing unusual.
 
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It is extremely interesting that this problem has developed after all these years. I think you landed on the reason though - something has found you that has managed to defeat humans... this is how the world will end! haha! Is this string algae on the rocks? Green algae in the water? Combination of both?

Like @JamieB suggested, I would add plants to the equation if you don't already have them. Let nature do her thing. The other thing missing from the system is fish - could you add a few goldfish to your pond? The fish will feed the plants, the plants will eat the excess nutrients in the pond and everyone will be happy!

But in addition to that, I'd suggest two things - the first is sodium percarbonate. This is a powder that kills single celled algae on contact and is harmless to wildlife. I've used it in my pond full of fish for years. When it comes in contact with water it breaks down into hydrogen peroxide and soda ash. It's sold commercially by pond companies under various labels, but it's all the same thing. Shut off the water, remove as much algae as you can by hand (especially if it's thick, string algae) apply the powder while the rocks are still wet, wait 20-30 minutes and restart the water flow. The algae will be gone in 24 hours. If it's a lot of algae, you may need a second application, but it works great. I suggest you look for the product NOT packaged as a pond product as you will pay 10X more if it's sold for ponds. I buy mine from a soap making supplier.

I should add that you could just try straight up hydrogen peroxide - it's cheap, safe, and easy to get. Turn off the waterfall, get yourself a few quart bottles of the plain old drug store variety H2O2, dump it all over the algae, give it time to work and then turn the whole thing back on. You can't use too much - it's very mild stuff. If that works, you could move on to the sodium percarbonate for the future.

My second suggestion would be to simply shut the whole thing down on a nice, hot, sunny day and let the sun bake it until it's dead. This may take more time, but any algae that depends on water to survive will die when the water is removed from the equation.

We would love love love to see your pond! Post some photos when you get a chance!
Did you see the photo of my waterfall?
 
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Actually, the right end of the pond which gets the most shade is the worst place in terms of algae growth.
I have been thinking about a possible solution to my problem. I drained my pond today and repeatedly (five times) partially refilled it each time always spraying the sides and bottom with a garden hose until I got clear water. But in addition to the green algae which I was able to only partially remove with the garden hose, much of the sides and bottom are covered with a black mass which I suspect is dead algae but harboring live algae beneath. My pond is concrete covered with a layer of sand colored, textured concrete. But, I am thinking that a possible solution is to have the landscape architecture company who built the pond and waterfall and has maintained it come in and apply another thin layer of the colored, textured concrete over the entire surface of the pond, thus, sealing off all the algae now on the surfaces of the pond. Any suggestions as whether this might work would be welcomed.
 
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I do see the photos - thanks!

Maybe have someone come and power wash the whole thing - a garden hose won't give you enough force to clear off the algae. I don't know that you'd want to "seal" algae between layers - in fact, I'm sure they'd clean the entire surface (probably with a power washer) before applying another layer.

Sodium percarbonate is a powder, but you just apply it to the rocks. No need to get in the pond. Just sprinkle it on the damp rocks and let it sit and do it's thing. But maybe I'm missing the problem - is it the algae on the rocks that is bothering you? Or in the actual basin? Do you have any pictures of the waterfall with the algae?

It's also possible that something about your source water has changed - I'm assuming you fill this with water from your house?
 
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I don't know why you are so opposed to adding plants.

Water lettuce and water hyacinth ( both are floating plants) will give your pond some surface coverage blocking the sunlight from getting to the algae. Plus both of those plants will thrive on the excess nutrients which the algae are feeding on. Basically starving out the algae.
It's a natural and very effective way of fighting algae.

Look at my water lettuce and water hyacinth...
20200918_152712.jpg
 
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Bruce, you are a retired scientist. Use the scientific method to solve this problem. Yes, plants, chlorine etc. will help but none of that will get to the root of your problem. Something has changed. Perhaps your new pump is underpowered. Possibly your water source has changed. Call your water company and see if anything has changed in the past year or so. Perhaps they are drawing it from another source. Get a current water report and compare it to one published by them a few years back. Perhaps your pond has a crack and crud is leaching in. Possibly a lawn or landscape service in your yard or an adjacent yard is using a different application and sending excessive nutrients into your water. The problem is solvable. Something has changed. So, what is it?
 
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I'm thinking you must not be adding a very large dose of chlorine tablets if the wildlife is drinking the water. So the amount you are adding is not enough to kill off the algae. Your friend wants you to shock it. Swimming pool shock is a grandular very high concentrated chlorine. I'm guessing you dont want to do that since everyone is drinking the water.

Is there a way you can put a net or something over the whole thing and then add the shock? The shock will dissipate after a couple days, but will probably kill off the algae. If you go that route, I suggest you get a good chlorine test kit to monitor when you can remove the net.

The thing is, the algae may just come back, so you need a more long term solution. Adding plants was a great suggestion. Add lots and lots of plants. They will starve out the algae by feeding on all the excess nutrients.

Blocking the direct sun will also help since algae is a plant. You can use plants that cover the water surface which will block the sun. Lilly pads, water lettuce, water hyacinths will all do that. The lettuce and hyacinth will also help compete with the algae by taking in the excess nutrients which is what the algae is feeding on. The lillies won't help much with the excess nutrients, but they can help to block the sun.
I keep one three inch diameter chlorine tablet in the pond (plus algaecide). What you say about the dose of chlorine may have some validity since I place the chlorine tablet at the far left end of the pond which is the most distant point from the pump which is located to the right of center of the pond and there is little or no algae at the left end of the pond around the chlorine tablet but all the algae at the right end of the pond well away from the chlorine tablet. But I do not want to place the chlorine tablet in the center of the pond close to the pump because my pond and waterfall contractors tell me that the chlorine destroys the seals of the pump. And, in fact, I used to place the chlorine tablet in the middle of the pond and did not have the algae problem but did have to replace the pump every 8-10 months. But, since placing the chlorine tablet as far away as possible from the pump, my pump has lasted two years so far, but, of course, now I have the algae.

As for placing a net over the entire pond and waterfall, I guess that would theoretically be possible but it would have to be large net to cover an area approximately 10 ft by 10 ft with an elevation of 5-6 ft. And, I assume that I would need to keep the waterfall running in order for the shock to work in the pipes, reservoir at the top and all the small pools of water on the waterfall. And, even, with a net, small animals and birds still would be able to drink.

I really do not want to add plants since it is such a small pond and we like looking at the clear water.
 
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I do see the photos - thanks!

Maybe have someone come and power wash the whole thing - a garden hose won't give you enough force to clear off the algae. I don't know that you'd want to "seal" algae between layers - in fact, I'm sure they'd clean the entire surface (probably with a power washer) before applying another layer.

Sodium percarbonate is a powder, but you just apply it to the rocks. No need to get in the pond. Just sprinkle it on the damp rocks and let it sit and do it's thing. But maybe I'm missing the problem - is it the algae on the rocks that is bothering you? Or in the actual basin? Do you have any pictures of the waterfall with the algae?

It's also possible that something about your source water has changed - I'm assuming you fill this with water from your house?
I am not sure power washing will remove the algae WHICH COVERS MOST OF THE BOTTOM AND SIDES OF THE RIGHT HALF OF THE POND since I have not been able to dislodge any of it with a rake or hoe, even on the smooth, level concrete bottom of the pond. When I drain the pond as I did two days ago, I can remove all the green algae that is visible with a garden hose but what is left is a hard, black mass on the bottom and sides of the pond (dead algae?). But, I suspect there is live algae within this hard black mass.

I still am not sure how I could sprinkle sodium percarbonate powder on the walls and bottom of the pond without getting into the pond, especially the back wall of the pond. I cannot bend over very far and absolutely cannot get down on my hands and knees. Well, I could get down on my hands and knees but could never get up.

Yes, the water source is the town water.
 

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