ALGAE—especially tenacious filamentous string algaes or blanket weed—can quickly turn a water garden into a battleground. I have been enjoying, and managing, two in-ground, rubber-lined garden pools for more than 25 years, and you know what?
It’s not that hard, despite the sometimes-tenacious, gooey green stuff. And most important: There is no other feature of the garden that brings more joy—or sustains more wildlife, from birds to dragonflies, salamanders to frogs–than a pool or pond. My essential spring water-garden care tips:
1. Reduce debris (organic matter such as leaves on the bottom of the pool), which adds nutrients to the water as it decays and can thereby “feed” algae growth. I always do this just as soon as the ice on the pool allows—typically in March—using a net, then turn the plumbing back on. (Details on filtration below.)
I leave a layer at the bottom for amphibians to tuck into, but not as much as a fall and winter of leaves blown in by the wind has deposited.
I make another pass with the net and my hands in April, once the perennial water plants start to sprout so I can see which parts are alive and dead, removing the latter, but being careful not to disturb masses of frog and salamander eggs. That’s a pile of dead plants and leaves at poolside scooped out last weekend, in the top photo, and a spotted salamander below in my gloved hand. I discard the smelly, mucky debris around shrubs; they seem to enjoy the treat.
2. Excess nutrients can also enter ponds in the form of fertilizer runoff. Are you feeding flowerpots beside a water garden, or is the lawn adjacent (and being fertilized)? Not good!
3. Think like the English, and add barley straw to your pond—whether actual straw stuffed into a floating sachet-like net bag, or one of the newer extract products (pellets, powders–both seen below–and even liquids). Barley straw helps make the water inhospitable for algae. The bagged straw sachets last about six months, the other products a shorter time.
4. Non-toxic additives can help. The last two years I have been experimenting with other non-toxic and/or biological additives (liquids or powders, sometimes formulated in combination with barley extract as mentioned; photo below). Depending on formula, they may help settle particles out of the water onto the bottom, and/or add enzymes and “helpful” bacteria, and I am favorably impressed, I think. According to label directions, these are added periodically through the season.
5. Changing the water, by the way, doesn’t work, and can actually backfire. Work to improve what you have, consistently keeping a vigilant eye out and adjusting things throughout the season.
6. Aerating the water (with a small spillway or waterfall, for instance) can help fight some species of algae, but not all, but is preferable to stagnant water for various other reasons. And who doesn’t love the sound of moving water?
7. Filter, the biological way. I have pumps and biological filters for both my pools (one in the water in my smaller pool; one external unit for the larger, like this). Inside biological filters, a community of helpful organisms including bacteria builds up on the filter “medium,” which is often made of foam or what looks like packing peanuts. The organisms help digest the unwanted pond wastes. Highly recommended. My units have each lasted many years, though every so often foam inserts may need to be replaced.
8. UV “clarifiers” can help, too. Some pond filters incorporate the use of ultraviolet lightbulbs. When the water passes by these “clarifiers,” or “sterilizers,” as they are called, algae buildup is prevented. Independent clarifying devices—not housed within the filter box—are also available at pond-supply vendors.
9. Critical: Shade the water (at least one-third of the surface should be shaded, some experts say; I shade most of the surface of my sunnier pond). Ponds in full sun will be most challenging to manage, and algae will romp. Shading can be accomplished by (surprise!) siting your pond in part shade, or planting shrubbery or grasses or other shade-casting things nearby. Most important and easier:
10. Floating water plants will shade the pond surface (and some also help with overall water health besides blocking light that would encourage algae). They are essential; I order by mail from Waterford Gardens or Pond Plants Online but there are many such sources. I love tiny Azolla, for instance, called fairy moss, and slightly larger Salvinia and even tiniest duckweed (Lemna). You might prefer big, bold water lilies, or towering pots of large-leaved elephant ears. Note: Never put water-garden plants into natural waterways, lakes, ponds, etc.
11. One more shading tactic: non-toxic black water dye (sold as a powder or liquid; the powder seems far more concentrated), which I also like because it helps hide the submersed plumbing in my small pools. I’d use it for that reason alone, though various labels also claim it reduces light in the water. The dye lasts a few weeks or a month, then needs to be reapplied.
12. If floating foamy-looking or stringy algae does occur, reduce it promptly. You can use a net, but I do it with my hand, moving in a swirling motion to gather it into clumps. Squeamish? Use a bamboo cane in the same motion.
13. Net the surface in fall, or not? Experts advise placing a net over the pond in fall to prevent debris from re-entering the pool, but my frogs, birds and other pond visitors and residents would strongly object (and even potentially be injured trying to navigate such netting).
14. Speaking of the other end of the season: Follow my fall pond-care steps, which do not include water changes and scrubbing the liner. They do include keeping a hole open in the ice that might form on the surface, to prevent buildup of gasses under the surface (and also welcome wildlife who want to drink or bathe 365 days a year).
This may be a silly question but did you have to stock your pond with the frogs and salamanders or did they come naturally?
Not a stupid question at all, Jen. Good that you asked — a lot of people do. Amazingly enough, they just showed up — in the very first year of the water gardens, in fact. They have all bred in the two pools every year since — several frog species, two salamander species, dragonflies and more. Delightful!
How do you keep snakes out or is that not a concern of yours? They scare me to death.
Hi, Susan. I am afraid of them, too, but I have worked hard to get past that feeling and welcome and love them. Best pest control experts ever: snakes. Some eat slugs, others eat rodents, etc. So I live and let live and try not to scream when one surprises me. : )
When you say to never put water-garden plants into natural waterways, lakes, and ponds, would this include ponds that don’t have water flowing out of them into a waterway like a creek? We have a ‘land-locked’ pond on our place that I’d like to add water lilies to. Can you explain more about why I shouldn’t?
Hi, Deborah. Good question; I should clarify. Many water-garden plants are invasive, especially non-natives that thrive in some zones and take over natural areas. So we need to do research before we “plant” them, just as we would in planting potential invasives in the soil that might “escape”. We have native species of waterlily in many areas of the US — but water-garden varieties may be non-native species that can overrun the others if set free (and many water plants get “relocated” on the feet of waterfowl, for instance). For instance, this bulletin from the state of Minnesota, explains the problem. If you want to use waterlilies other than in a pot in a contrived water garden like mine, you can shop for species that are appropriate for your area (I’m not sure where you live). I think it would be good to ask your local cooperative extension or better yet perhaps your DEC…start by searching for a similar bulletin to the ones I showed in the links — one for your state. I don’t have the degree of expertise to know how waterlilies specifically do or don’t escape from a landlocked pond.
When can water plants be added? I am in Southern Ontario.
Thank you!
Hi, Patti. I usually order them just as the weather starts to stabilize, to put them out when night temps are above freezing. So here my final frost date is technically about May 20 give or take, and I might put out water plants a little bit before that–maybe early to mid-May if the 10-day forecast looks stable.
I have had a pond for 4 years with one large potted water plant and I do buy water lettuce to cover half of the pond but in those years I have only seen 1 frog. There is a small waterfall and we use another water feature which the birds love to fly thru.
Although my nursery sells frogs I don’t want to go this way but would love to see frogs enjoying the pond. Any ideas on how to attract them naturally?
Margaret, are unwillingly share the brands of non-toxic water clarifies you use in your ponds?
Ugh, spell check took over my previous post. Should say are you willing to share brands of water clarifiers that are non-toxic?
String algae is a constant problem, I found that twirling a long handle bristle brush(toilet bowl brush) works great
Great idea, Pat. Thank you!
I don’t have a pond, but I do have a large bird bath which is too heavy to turn over and dump out. Is there anyting I can add to it to keep it clean(er)?
A mink got into the open hole in our pond this year and ate every fish. I’ve yet to see any frogs this year, either, though I cleaned a couple of dead ones out last week. I’m concerned about restocking the pond as I’m unsure how to control/live trap the little critter. I actually took photos of it never putting 2 + 2 together on that one! Any suggestions?
Hi, Sharon. I’d contact DEC or a licensed wildlife expert approved by them to get advice and perhaps help. (The latter are often in the Yellow Pages under wildlife control, but I think it’s better to ask a public agency for a referral or advice first.) It’s unsafe and illegal to interfere with wildlife, and minks are tough guys. I suspect he/she will be back with the good pickings in mind, so it’s a good moment to inquire.
Margaret–you are a pond woman after my own heart. I agree with your advice 100%
I just put in a pond with a small waterfall this June, and it has made my garden come alive! I’m stocking it with native aquatic plants. I already hear a tree frog in the evening, but haven’t seen it yet. And the bird population in the yard has exploded. What a joy!
It wasn’t difficult…but I did lots of research first. Then it was just a matter of hiring someone to dig and help me lay the liner. Everything was ordered on line except the flat rocks for the edging, which I ordered from a local landscaping materials company.
We had a manmade stream &waterfall in our last garden. Initially had big problems with string algae till I sprinkled water cress seeds @ edges of stream. Up came the cress and the string algae turned to slime & sloughed off. Never had a problem after that. I’d seen a little in early spring till the cress came out then it would just disappear.
I use Skippy’s pond filter which you build yourself. It eliminates most algae, keeps my pondwater clear, cost little to build, and is chemical free. Best ever! Google Skippy’s pond filter.
Interesting, Debra. I think I could have saved some $$$ after my longtime filter just imploded and I ordered a new one! :)
I spent lots of money trying to keep my pond clean before I built the Skippy. I have used it for years and its been great! I still get minimal string algae but that is easily scooped out. Oh and you never clean the Skippy….another awesome plus!
I don’t have a pond (I wish I did), but do have a very large turtle who lives indoors in a 150 gal. trough. I built a Skippy’s filter for her tank. Turtles are notoriously dirty, and her water is always perfect and, as previously mentioned, I never have to clean it! Win, win.
Love it, Beth–wish I had a turtle, too!
I have a pondless stream. this is the second year of operation and found string algae showing up this year. After a bit of reading I found Hydrogen Peroxide added to the water seems to inhibit the growth, & It’s harmless to the wildlife. I’m treating it with a quart per 500 gallons weekly till it’s totally under control. Then will cut back to everyother week. Can buy it at local grocer 10qt’s for $10. Seems to be working.
Bob
My small artificial pond is covered with duck weed. I tried to get rid of it – no luck. If I pulled it out it would grow back in a day. Then I looked it up and learned it is the best natural water filter. The pump in my pond has not worked in years but the duckweed keeps the water pure, and the frogs and snails love it.
Lucky you (except you didn’t know it, right?). The garden and nature are funny that way; sometimes what looks like an “issue” is a blessing in disguise. Yes, shading the water this way and letting the floating plants do their thing is the best purification, I think, too.
if anyone wants some duckweed I am happy to share
The first year we had our pond, which is about 8 X 12, I was delighted with the masses of frog and toad eggs that just appeared. Then they hatched. The swarms of tadpoles quickly overwhelmed the limited environment. It was nightmarish. The fish could hardly breathe or move. Ever since then I have carefully removed as many of the egg masses as I could as soon as I see them. I relocate the eggs down to the stream that crosses our property. I know that a great many escape my net and hatch anyway, and that’s OK, we can handle a few hundred. But not the thousands.
I agree with Bob about hydrogen peroxide, though I only add it if the water seems to be getting greener than usual, and I only need to do it once. The “magic” behind barley straw, BTW, is its production, on the molecular level, of hydrogen peroxide.
One of my most magical moments with our pond was spotting a dragonfly larvae haul itself up onto a lily leaf. It then morphed into an adult right before my eyes, almost like time lapse photography. When the wings dried, off it went. I hope to see it happen again someday.
What do you think of growing edible plants in the pond? I don’t use any chemicals but do have a biological filter and I add 2 barley straw bundles it my 2500 gallon pond each spring. I was thinking of water cress and wondered if it would be safe to eat. I’d love your thoughts on that and other plants that might work. I do have goldfish, koi and frogs. THANKS
We’ve had a man-made fish pond and waterfall for about 13 years. It’s had its delights and disasters over the years but last year was our first visit by a large snapping turtle ( there’s a nearby 9 acre pond). It lurked under the water lily leaves for several weeks and I was fearful that it would eat our lovely Shubunkin goldfish that would swim obliviously in front of it. Finally I thought maybe it couldn’t haul itself up the sloping rubber lined sides of the pond so I piled up rocks to form a ramp. My husband scoffed but after a few days the turtle was gone. I’ve read that the older snappers are probably too slow to grab fish and they mostly eat decaying plants. Still, I’m hoping it stays out of our small pond this year.
I’ve never had a snapper here but years ago occasionally had other smaller turtles show up temporarily.
Hi Margaret ~ I put in a little frog pond last summer, mostly in the shade and I
don’t use any filter. I put a few plants in the gravel and finally the last part of the
summer the water was clear. I ordered the donut things for mosquitoes.
I might try to make it a little bigger early this spring, it’s only about 15 gallons.
Love your info!!
The water gardens are my favorite thing I ever created here. Endless enjoyment, and fascination. I vote for bigger! : )
2 years ago a huge snapper showed up in our 15 x38’ pond. We have no idea how long he was there but he was very difficult to catch, regular large nets were too small to fit his body so we got a large deep sea fishing net. It took 3 of us to finally capture him. Last year a smaller snapper (about 14”) showed up and I now realized when a snapper gets in the pond the frogs stay close to the edge and the fish act weird.
You can have a snapper and never know because they don’t come out to sun themselves like a paint turtle does and when they come up for air sometimes it’s only the tip of their nose comes out of the water.
Yes, we had some fish missing and the ones they ate were the beautiful electric blue ones. Must of been the color he saw.
Haven’t ever had one waddle uphill here and visit the little pools, Kathy, but I do see them crossing the roads nearby of course.
Margaret, no mention in the article about fish. You do keep them don’t you, or is that too much for our 5b winter? I know folks over in Hudson who send their koi to a “winter resort,” professionally maintained in Albany. Yipes! Out of my league!
Always, thanks for your blogs.
Hi, Jan. I did have fish (comets, a very hard goldfish-like creature) for many, many years. Finally a year ago the last several of them got murdered by a very determined raccoon. As long as your pool is big/deep enough (like 1000+ gallons for koi and 3+ feet deep — not a little shallow pool, which some smaller fish species can tolerate) and you keep a good sized hole in the ice for gas exchange all winter and stop feeding when the water temp dips below about 50, you can keep fish. Some of that is explained in the winter pond care article. I have found the owners of Waterford Gardens in NJ (they have been in the pond plant/supply/fish biz for a very ling time) to be helpful when I have called with questions about specific breed of fish (or plants). I did have koi early on
Very informative.. timely too. My koi ponds opens today…
So helpful, as usual. Thank you for all the info you share!
You may not net but I find it necessary as we have herons both blue and green and mink river otters and raccoons , The net helps but I have had my fish and they’re big disappear overnight.
Thanks for the tip, Judy.