springtime water-garden care tips

removing leaves and dead plants from water gardenALGAE—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 20 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:

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 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.

Spotted salamander, Ambystoma maculatum

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)?

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.

Non-toxic additives: The last two years I have been experimenting with other non-toxic and/or biological additives (liquids, powders, sometimes formulated in combination with barley extract as mentioned; photo below). Depending on the formulas, 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.

Barley and other natural biological pond additives

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.

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?

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). Inside biological filters, a community of helpful organisms including bacteria builds up on the filter “medium” (often made of foam or what looks like packing peanuts) and helps 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.

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 is prevented. Independent clarifying devices—not housed within the filter box—are also available at pond-supply vendors. I seem to manage without these, but in a large, sunny pool I think I might rely on one.

Critical: Shade the water (at least one-third of the surface should be shaded, some experts say). 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:

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 love tiny Azolla, for instance, but 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.

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. The dye lasts a few weeks or a month, then needs to be reapplied.

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.

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).

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 365 days a year).

April 23, 2013


  1. Jen V. says

    This may be a silly question but did you have to stock your pond with the frogs and salamanders or did they come naturally?

    • says

      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!

    • says

      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. : )

  2. Deborah B says

    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?

    • says

      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, or this one from Washington explain 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.

  3. wendy cleaver says

    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?

  4. maddybee says

    Ugh, spell check took over my previous post. Should say are you willing to share brands of water clarifiers that are non-toxic?

  5. Pat says

    String algae is a constant problem, I found that twirling a long handle bristle brush(toilet bowl brush) works great

  6. Judy says

    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)?

  7. Sharon says

    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?

    • says

      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.

  8. Joan Martorano says

    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.

  9. kate says

    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.

  10. Debra says

    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.

    • margaret says

      Interesting, Debra. I think I could have saved some $$$ after my longtime filter just imploded and I ordered a new one! :)

      • Debra says

        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!

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