I used to always have a lot of algae in the spring when I topped up the water in the pond. The last two years, I used only water from the rainbarrel, and there was no algae bloom.

Hi
I think the ONLY way to keep algae at bay is the way ma nature does ,Lots of plants !! They will use up the nutients that the algae need .
Are you talking about attached algae or suspended /greenwater.??
What is your water source. Many municipal water supplies are loaded with nitrates and phosphates right out of the tap. Prime algae food lol.
The rainwater USUALLY has far less . I use a rainwater purge system on my above ground pool with only an occasional top off from the hose. no algae but can lead to very acidic water which isn't too good for the usual pond fish.
Find what plants will grow well for you both floating and submerged Makes for a far prettier pond anyway?? gary

UV light works miracles with algae

Marsh marigold is one of the earliest plants to sprout in the spring. It will outcompete the string algae and the suspended algae for excess nutrients and solve both problems.

Over the years I have found the best way is to keep the bottom of the pond clean, use lots of veggie filtration,provide shade in the form of floating plants and or floating islands and perform water changes as needed- but only as needed.

Lots of plants always help. Rock salt is not for getting rid of algae. A samll percentage (like .2%) is good for your fish but adding too much will kill your ifsh and your plants. I use Goldfish Koi Pond Powder (calcium bentonite)..cheap, all natural and safe.. from the site below

Here is a link that might be useful: The Pond Site

A cheap fix is Hydrogen Peroxide. The stuff you get @ Dollar General, a 3% solution. Pull out as much as you can with a toilet brush and then pour on the Peroxide. It literally melts the algae. ANd there are no harmful side effects for the pond. Just don't pour it directly on plants. It will burn them.

I agree with Pat. H2O2 works like a charm on string algae but not other kinds. I use one pint per 1000 gallons but you could go higher without causing problems. Try the lower dose first.

Thanks I will try the peroxide.

We've had terrible string algae the past 2 summers, last year being worse. We tried barley, and some chemicals - I've told my husband NO more chemicals!

Will hydrogen peroxide harm my fish? It's been so hard to keep fish, what with the heron, etc and I've had these for 2 years now.

H2O2 is water with one additional oxygen molecule. It won't harm the fish unless you pour it directly on them. Then it might temporarily bubble away the slime coat that fish have. It is sometimes used to add oxygen to the water but takes a lot. I have used it directly on a fish that had an infected injury from a heron. The wound healed up very quickly after that.

There are many uses for it. Do a Google search if you are interested.

I kept goldies for years and used peroxide and never had a problem. I used to turn off the waterfall and pour it directly no the rocks to dissolve the algae there. Used as many as 4 bottles at one time. Then I started up the pump to wash it away. Again, do no pour it direcly on plants and fish and you will be fine. And, I believe it is much safer than the "store bought" concoctions which are expensive and full of harmful chemicals. I used Algaefix for a few years and killed all my snails unknowingly.

I was thinking of using the peroxide method but my pond is still in its winter stage. The pump is shutdown. Do I need to start the pump? Do I mix the peroxide and pour it around the pond with the pump off. Need help the string algae is consuming my pond. I have had the pond for 11 yrs and have never had string algae. It started at the end of last season but I thought over the winter it would die off. Any ideas why it would start now?

It could easily have been brought in by a bird but the spores from algae are literally every where including fish food, potting soil, plants and the air. It is impossible to guess the source. Your pond just happened to have the right conditions to cause a bloom although it usually grows more in warmer conditions. Winter growth is fairly common, just slower.

First remove as much as you can reach with a new toilet bowl brush. Cheap, good size and shape, won't harm the liner, collects algae very well and is easy to maneuver. Broken off pieces of string algae are easily sucked up by a pump which reduces the chances of it starting to grow again. Filter material such as poly quilt batting does a good job of capturing the debris and is cheap enough to toss when the problem is gone or you can pour some peroxide on it and continue to use it.

You can pour the peroxide on full strength. Diluting it only reduces its effect. It becomes inactive(changes to water, releases an oxygen molecule) in minutes or even less. Applying it at the sides and around the waterfall are best. Since string algae is very prolific you will likely have to do this again as the weather gets warmer.

Other than appearance and growth rate, string algae isn't all that bad for the pond. Fish and other critters will use it for their eggs and will eat it. It makes a good addition to the garden as mulch or in the compost pile.

I always get a fair bit of string algae in the spring when the ice goes out. Then, as the plants kick in, the nutrients available for the string algae are used by the plants. There is still string algae in summer but it is limited.

it's not a natural method but I sprung for 2 uv systems and my water is perfect after 2 weeks. Before you couldn't see down for even an inch. It's a bit expensive but if your pond is under certain conditions that promote algae like mine (direct sun) it's worth it in the long run.

More plants mainly waterlilies to cover the surface so the sun doesn't get through to the water and the water lilies will eat up all the nutrients the algae needs to grow and it will slowly die off. Trust me it works and your pond will be alot healthier for it and your fish will be happy and healthy as well. I have 10 water gardens it works.

Here is a link that might be useful: Make Money Gardening

Chemical fixes will work a while, then the plants, bounce back...

Algae is a fast growing plant which is well able to take advantage of fertile water early in the year.

Take a leaf out of nature's handbook, let loose a plant which is more ruthless at extracting fertility and dominating a pond...

Azolla will dominate the pond surface, shade the algae, deplete the ponds fertility and is much easier to get rid of when the algae has been more or less exterminated

Azolla is a very efficient fertiliser when it has done its task and needs thinning out. Plonk it around drought prone plants as a mulch...

Send it to me. I may be all wet but I've noticed that when the string algae takes off the suspended algae clears. Maybe it's a coincidence but I am happy when I see the hairy stringy stuff. :) But then, my fish keep it trimmed back pretty well so it's not a nuisance, and it's the only plant I can have in the pond (because of those bad-mannered fish.)

As an experiment I left a tub of fertile water do its own thing, while I can't remember the sequence, at times algae would over run it. Duckweed bumped it off. Water meal over run it. Bladderwort choked it.

Whatever you do, a fertile body of water is going to be colonised, invaded by some resilient plant. I quite like the sort that are easy to sweep out, all in one go, or a mix of plants which you do consider picturesque... (ornamental)

So UV lighting kills string algae...can you place spot lights that are UV on the direction of the problem?

Or the peroxide...turning off falls and cleaning. How soon before you can turn the water back on?

This won't harm birds then since it won't hurt fish.

UV lights do NOT kill STRING algae. UV, when properly sized to your pond and when the water flow past the light is correct is an excellent control for free algae, the kind that turns your water green. String algae is attached to some part of your pond and will not flow past the UV light. UV is only effective if the water flows within about 2 to 3 inches of the light and must be exposed for a certain period of time. It the water flow is too past it won't kill the algae.

Thanks...it is a problem with our waterfall. It is a vanishing waterfall so no real pond. Enough water to wet the dogs feet at the base.

So peroxide won't hurt the birds once falls are turned back on? Really don't want to kill wildlife which visit frequently.

I came here to say that the uv filter is extremely efficient removing the floating algea however it does not appear to have any effect on the string algea. There's a ton of string algea in my pond now. I have pond plants also but still there is algea. I am going to research more about using hydrogen peroxide, that sounds like a cheap fix.

Algae control is as easy as A-B-C 1,2,3 - R

Calcium bentonite [Koi Clay] works very well at killing and suppressing algae growth, but first:

1. If your pond has a gravel bottom you may need to debulk the nitrogen and phosphate load first by pressure washing string off of the side wall rocks and and the using lower pressure with more volume to wash the muck down to the lowest level where you can sump pump it out to the benefit of your gardens and trees. I did this in early June [after a few year's hiatus] and my ponds water has remained nearly crystal clear since, just from that.

2. After your water has stabilized, ~ 24-72 hours, depending upon your filtration method, you may reintroduce your Koi, and resume normal feeding cycle, using extra caution to avoid overfeeds, prevent over wash heavy rains, which can raise nitrogen and phosphate levels.

3. Then you must decide you methods for long term string algae control. control that and you won't have any of the other stuff in significant amounts to worry about.

A. Netting, removes string and removes its incorporated nitrogen and phosphate out of the ponds biochemistry. If you wait until you have a lot it is hard on your back and the results are as a whole unsatisfactory, but it is easier to debulk living string or blanket weed while it is a live and buoyant, than after it has sunk to bottom and is doing a good job of starving your Koi of critical oxygen. So, net what you can and kill the rest, while upping your preventative methods.

B. Chemical algaecides [non copper containing, so that snails and crustaceans remain unaffected], not only kill visible string algae, but its spores and initial growth

Sodium carbonate
peroxyhydrate essentially harmless to plants, fish, and other aquatic fauna is spread over the surface wherever filamentous [string, blanket] algae are found and sinks down onto their strands for a very potent contact algaecide, but as it dissolves does and equally good job on planktonic free floating single-celled algae which cloud and color water green, ultimately turning your pond's water into thick pea green soup, if you nitrogen and phosphate levels are high enough.

PAN [Poly(oxyethylene) (dimethylimino) ethylene (dimethylimino) ethylene dichloride], the active ingredient in Algaefix, though it must be used with some caution not to overdose or you may lose Koi. Some web essayists have made much of the LD50, of Algaefix, and it is important to remember this when using the product, but the LD50 of many therapeutic drugs necessary for survival with some diseases is not much different than Algaefix for your Koi. If you must use, use wisely!

C. Calcium Bentonite marketed as Koi Clay at /substantial markup/ is mined as diatomaceous earth and proves toxic to both filamentous and planktonic algae and also serves as a flocculant binding small debris-particles which then sink to the bottom or become processed by the specific biofilter utilized. Calcium and other trace elements found in powdered calcium bentonite improve Koi color and plant health, such that the ponds circulation and natural nitrogen cycle provide everything your fish, small creatures like frogs and snails, water lilies, and other aquatic plants require to grow. Making the addition of plant 'fertilizer' unnecessary and counterproductive visa vie the algae issue

Remove dead aquatic material and debris before it breaks down and enters your pond's Nitrogen cycle, or you will have plenty of string algae to remove later, no matter what you do.

Happy Ponding!

UV- forgot to add this.

UV carries an expense for both electricity and the replacements UV bulbs, tubes and gaskets. Properly sized, a UV tube loses its effectiveness after about 1.3 seasons before, it must be replaced.

Think Generic: Bulk Bentonite 16-50# can be had for the cost of 2-3 containers of the Koi Clay Brand. It's just as amazing when you compare branded and generic drugs for human use. If you purchase a bulk order, a single purchase, ~ $16-$50.00, will last 5-10 years at a fraction of the cost depending on the size of your pond and Bentonite is the only solution for extremely large ponds of more than 10,000 gal. For those large ponds or those of you with a heavy hand, other than adding to the cost, you cannot really over-treat with calcium bentonite, since you are in-effect just adding a powdered-clay [as fine as talcum powder] to your pond. The more you add the cloudier the water, but even that clears after 1-2 days, depending on the surface area/volume of your biofilter and how fast your pond turns over its volume.

Comparing the total benefits to your fish and plants:

Bentonite beats UV

UV only kills the algae that get pumped through its field. It has no effect of established algae strings unless they are dislodged, but its remaining strands will regrow, unless killed-off the rocks, etc. entirely, by some other systemic treatment. UV plays no role in the nitrogen cycle and has only a minimal role removal from you pond water. Calcium Bentonite kills algae, as it strengthens your plants and fish. Strong healthy fish consume some algae, while your plants remove considerably more soluble nitrate from your pond's nitrogen cycle, as they grow more vigorously in the presence of added calcium and rarer minerals and contained in bentonite clay, in addition to the nitrogen present.

Having enough plants and cutting them back, removing their remains at seasons end or very soon after the spring thaw will dramatically reduce your pond's nitrogen /and phosphate/ load, which can be composted into your gardens reducing your dependance on fertilizer there. Eventually with a little trial and error your reach as steady state with clear water season to season, as you achieve a proper balance of your open ecosystem: with some plant material plus koi food, and the occasional snail or frog from outside bringing nitrogen into your pond's ecology and nitrogen cycle, and the removal of plant material and other nitrogen-rich detritus from your pond, before it decays striking an algae-free balance.

Hi there, just looking at my pond and definately dealing with a string algae problem. What are the dosing guidelines to follow? And can I do all this while my fish are still in their somewhat winter stupor :)

Hi Christina - what dosing guidelines are you referring to?