The first thing you did wrong is clean the algae off the sides on the pond. This algae is an important part of the pond ecosystem. It competes directly with the free-floating algae that make your water green. By making your pond spotless, you undid all the maturation that your pond went through in its first season and started over from scratch. But now you had a few "green water algae" that had no competition from the ones you scrubbed off the walls -- so they grew like crazy.

It's great when you do a spring housecleaning on your pond -- removing dead plants, repotting others, vacuuming the bottom, changing the water -- but don't mess with the wonderful water-cleaning ecosystem that grows on the sides of your pond.

Fish plus no filter probably contributed to the algae bloom, and your filter should help some, but for the most part green-water algae grow when they don't have competition. Your best bet is to let your pond mature. And don't put anything in your water but dechlorinater and a little fish food.

Scrubbing the sides of the pond is not a good idea, that algae is "good algae" What you did was reset the cycle back to "new pond" and now it has to grow new algae and cycle again.

Ponds are supposed to have algae. They are not supposed to be spotless.

You can buy an expensive UV light but you will still have algae, it only works on suspended algae not on hair, carpet or string algae.

Having lots of plants and patience are the key to pea soup algae woes.

Thanks to all who sent help posts...I have a few more questions about what Im doing wrong...I can see that by cleaning the walls that we got green algae but also got pea soup...we put the barley bales in, which is this a good thing?..we didnt wait for a very long time before we took about a 1/3 amount of water and replaced it with clean and added a declorinator...I thought maybe if we used a liquid barley/peat liquid and thats when I saw the new green algae that was on the sides started to go away...did we kill it with the liquid barley?..Im so confused but I think Im learning....

Algae comes and goes for lots of reasons.

You can think it was the barley if you like. The first study on barley effect on algae was done by Newman, JR & Raven, 1993. That is the study sellers of barley cite. Under lab conditions Dr Newman saw a small reduction in algae growth. Even this best case study did not see algae actually die. It just grew slower.

Follow up studies, or reviews of studies were done at the following universities and found barley had no effect, or so small it couldn't be determined, on algae.

Iowa State University
University of Florida
University of Nebraska
Maryland Cooperative Extension
Purdue University
Ohio State University Extension

Barley sellers don't cite the follow up studies.

But if you like buying barley and putting into your pond I say super. It's a hobby, have fun.

A properly sized UV will clear the green "pea soup" water within a week or so. Lots of plant cover will also help, but will work a lot slower, perhaps months. If it's small enough, you can erect one of those 10 x 10 picnic canopies over the pond to create shade and deny the algae sunlight. Lots of floating plants, like water hyacinth (if they're legal in your area) will also help.

A carpet of aglae on the walls of your pond is a good thing. Don't scrub it off! You obviously don't want the long string or hair algae, but that short carpet harbors all kinds of good things to keep your water clear and healthy.

I never, ever, ever do a complete cleanout of my pond. When you do that, you totally destroy your eco-system. If your pond is overstocked, it also may be more difficult to keep the water clear and clean.

I am converting my large pool into a pond. With the wonderful help of my son and grandsons. We have small fish from local creeks thriving amd reproducing. Problem is water going very greenynbrown and little local water lilies don't last more than couple of weeks. How do I clarify the water, just a little (I know as a pond it will be colourful) LoLol. Also couple of ducks infrequent visitors. Housing estate has destroyed local creeks and billabongs so wildlife getting desperate which is one of the reasons I converted.

Water very murky. Help!!

More competition might help. My pool-pond is way clear now. I got one water lily which is struggling (probably should plant it instead of growing it as a floater), but I also got water hyacinth, water lettuce, parrot's feather, anacharis, duckweed, azolla, and some moss-like algae that grows on stones and on the sides.

No filtration, no UV sterilizer, not even a pump. No shade, and the plants haven't grown enough to be a cover crop yet, either. Just lots of hungry roots sucking nutrients out of the water. It's not an all-you-can-eat buffet for the single-celled algae that makes the water look like crap anymore.

It took some weeks to make a difference, and I'm still modifying it (slowly adding sand and gravel for recycling microbes to grow on, as I find time to clean it), but it's helping a lot.

Here's how murky mine was on September 24th.

This is how clear it looks today, just before leaving for work. Looking through about 3 feet of water.

Finally caught the minnow fry on camera. Not the greatest clarity demo what with the sky reflection, but more interesting than the foot of a ladder.

I guess what I'm getting at is, if you put in a bunch of different kinds of plants, and let them battle it out, the algae that make your water look like pea soup won't have such an easy time anymore, and you'll probably find SOMETHING that can thrive in local conditions, even if your first choice of plant doesn't.

Thanks Jon. I've decided on duckweed and azolla. Now just have to find where to buy some. As my pond is huge I reckon it the cover from sun that is needed.

I got my duckweed and azolla free. There's a koi supply shop a few cities away that sometimes gets them by accident, they consider them mild weeds and allow samples to be taken freely.

I'll have to check shops etc., out. There is eBay but not fussed with that. I'm sure there's stuff around jus have to do some searching.

Azolla and duckweed are natives and could be where you got your fish, particularly in billabongs. They prefer slow moving waters.

Azolla and duckweed look neat together when the water cools and the azolla changes color, contrasting its deep red against the duckweed's pale green.

Thanks. I'll let my son and grandsons know. Problem is it's been so dry, local creeks and billabongs not looking good. But, we've had a bit of rain and more should be coming now with the wet season.

Depends on where you are, but chances of above average rainfall are good for October in many areas but then drop off again for a while after that. I found wild ducks brought duckweed into one of my ponds, don't know where from though. Azolla doesn't seem to transport as easily unfortunately but I know where to get it.

I'm in sub tropical Qld. Spotted a lagoon with duckweed y/day in my travels. Looks hopeful.

With the weather warming up the plants should be multiplying like crazy. But once the rains set in they tend to get washed away, so your best chances should be now. I'm near Darwin myself.

We had a storm with heavy hail couple weeks ago and the few little native water lilies we had got kinda swamped and chopped ......sigh. I'm in Brissie.

They should come back okay. That's the advantage of natives, they've "seen it all before".

Hope so! Now the big frogs are knocking the pots in shallow water over! The stupid things can't seem to find where I've built brick steps for them

The joy of having nature in your backyard. Are you sure they're not cane toads knocking over the pots? You know what to do with them.

No, not toads! I've some of them but so many since crows discovered them! Lol Messy cleaning up after them tho. Big frogs are Parsons? Marsh frogs. Similar but able to see difference. My grandsons get stuck into the toads The sixteen yr old has webbed feet so to speak, into everything marine and creepy Crawley. We get a lot of snakes too.

Is that Pearson's Frog, Litoria pearsoniana, and the Striped Marsh Frog, Limnodynastes peroni?

If you have a lot of frogs around you'll also have a lot of snakes. Snakes like to be around frogs. Not so much the other way around. When you like nature you can't really take sides. I've identified about 16 species of frogs on my place and 10 species of snake. The only cane toads I count are those that go into the freezer.

Probably. My cane toads are in the drain down pipes. Gets very noisy. Lol. Always had snakes here as house backs onto cow paddock, down to creek then river. Although now they're building a housing estate nearer to creek. Totally displacing a lot of wildlife. I have a possum or two in downstairs ceiling. (Under lounge room). Have to mediate between them and my cat LoLo, Had a 6' vivid green tree snake top of back stairs one day. Had a tussle grabbing cat and sending snake back down, it didn't won't to go. Noticed lollies sending up new shoots, so hope they're coming good.

Hi! Please ignore my comment if it’s unrelated to this thread, however, this came up when I googled “deter algae on a flagstone fountain”. I believe my landscaper referred to mine as a “waterless pond”? It’s a tub that I must fill every couple days and is filled w/ large rocks. I was using w/ a weekly treatment that was noted to be safe for birds as they flock to both the pond and fountain for drinks daily. It had no affect on the algae. I began using the hydrogen peroxide method, but you’re correct, it must be kept up regularly and here in AZ the winds are unpredictable so shutting the fountain off and timing after “bird schedule” makes it difficult to create my own schedule. It does, however, work! So your answers have helped a bit (no idea good/bad algae), doubt if I could utilize pleco (sp) and/or plants since it’s not an actual pond. Was wondering if sealing the flagstone fountain would alleviate the algae from “adhering” or at least make it simpler to remove?

I'm no expert, but for a situation like that, I would try a lot of aquatic snails. They don't need much water, and might make good snacks for some of the visiting birds.

I agree, snails are good for that. I have some in bird baths which don't hold much water and they happily munch away on the algae. Always worth giving it a try.

I might try some snails in my shallow bird bath. Do the birds eat them tho? I really need some for my pond (converted large pool). Still trying to source surface cover!!

Thanks for the snail suggestion! Any input on the flagstone fountain, perhaps as to sealing to prevent algae from penetrating?

Algae is like one step away from the primordial soup of most primitive life, it's super tough because it's super simple. I don't know that there's any kind of sealant that would prevent it from growing on a surface, if there's moisture and nutrients for it.

If you don't need the algae for eco system purposes, like some of the posts mentioned in this thread, then for decoration pieces, you might succeed with some power-spraying now and then.

My pond (previous large pool) has gone ' rown' ??? The water that is. Fish are fine and multiplying. Frogs ok. But....plants don't last. Any ideas anyone?

What sort of symptoms are the plants showing?

Gradual dieback. Leaves go brown. The surface of the pots, which are just under water, get an oily sheen on them. Been trying to get surface floating plants like duckweed but no success. Have potted plants,flowers around edge of pond and water runs off into pond when I water. I noticed fish followed me around pond when I watered y/day evening, I think they were feeding off runoff.

If the fish and tadpoles are okay then there shouldn't be anything wrong with the water. What type of plants are they? Surprised you still haven't been able to get any Duckweed. What about Azolla?

Duckweed can only be gathered from local waterways. Nurseries not allowed to sell it. Wildlife, namely wild ducks finding it hard to find decent waterways due to developments. So they're eating the available duckweed! Not sure about Azolla. Will check it out. Put some rainwater fro tank in and I think colour is changing ok. Lot of rain also last couple days. Plants have new green leaves this morning. Next project is fish that will control guppies which are getting out of hand lololololol.

There are several species of Duckweed native to Australia and they're not classified as "weeds" anywhere here. Unfortunately some nurseries aren't aware of this and assume that having the word "weed" in their name makes them a weed. You can buy Duckweed online, lots of people who keep fish or turtles buy it to feed to their animals. There's one place here, Aquagreen, that specialises in fish and waterplants and sells a couple of species of Duckweed. They also sell Azolla.

Are those "guppies" what's also called "river guppies"? Actually a Gambusia species which was introduced to control mosquitos. Like cane toads they never did the job and have become an ecological disaster. About the only fish I know that would bring them under control would be Barramundi. You'd need a large pond for them once they get a bit older.

Guppies ok here in waterways. Will give Aquagreen a go. Many thanks. My 'pond' is large as it is a converted pool about 10x5 metres. I feel it just needs cover growing on surface.