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Pond Algae as top dressing?

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I have a pond that's a prolific algae farm. I'm always tempted to plop the algae around my veg garden plants. Can anyone think of a reason not to? Also, I often water with pond water. I figure it has all those bits of organic junk that might be enriching. But maybe I'm missing something. (This is my first season with a back yard or garden).
Thanks! Jessica

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  1. We often water with pond water and my SO likes to squeeze out the ooze from the filter on top of plants. I haven't seen any ill effects, but I'd be interested to hear if there is a reason not to do this.

    1 Reply
    1. re: calliopethree

      The filter is loaded with what are referred to as, "beneficial bacteria." These bacteria are critical in breaking down ammonia in multiple steps into nitrogen. While the bacteria probably won't do any harm to your soil - it may in fact help make nitrogen more available to your plants - wringing the filter may severely reduce the number of beneficial bacteria in your filter, thereby disrupting the critical nitrogen cycle. Your pond could experience spikes in ammonia, nitrites, and nitrates, which is really hard on your pond organisms. Your SO can try dipping the filter in a large bucket of water and swishing it around to loosen the goo. This will lessen the disruption of the established bacteria bed and you can also use the wastewater on your plants.

    2. Sounds densely nutritious to me.

      I don't have a pond. Just a jug large enough for a couple water plants. When I get sheets of green algae (at least I think it's algae) I pull it out and put it on my compost pile.

      1. my brother stopped using pond water to water plants in his greenhouse because it harbors fungus which can ruin plant roots. if you use the algae or pond water on your plants i suggest purchasing and using a good fungicide in addition

        2 Replies
        1. re: buckeyeville

          While the pond water might be introducing fungal spores, I think it's the higher soil temp in the greenhouse that provides the perfect climate for encouraging the fungal growth.

          1. re: buckeyeville

            Plant fungal diseases are not harbored in pond water. As bulavinaka says, temperature and humidity plus the presence of fungal spores gets fungal diseases going.

          2. If your pond is having an algae problem, then you are most likely having an excess nitrogen issue. I don't know how large your pond is or what organisms are in it, but issues like runoff or excess feeding are the usual suspects. If you have fish in the pond that you feed, the number of fish in the pond may be too many given its size. you might also need some/more filtration/water circulation, as well as other critters like snails to help control the algae. Also look at how much food the fish are actually eating - uneaten food that settles to the bottom is just fertilizer for algae.

            As for using the algae, I'm assuming it's what is often called hair algae. It probably won't cause any problems in small quantities/used infrequently. The problem with large quantities/frequent use is that it will form a solid mat which will hinder moisture from entering your soil from above, as well as reduce respiration. I would try composting it first to see if you have any success in breaking it down.

            1. Incorporating rather than using as a mulch is preferable.

              1. Update on the algae:
                I wrestled with algae blooms all summer. It's a small pond with lots of nitrogen-hungry plants and fish that I do not feed. Their job is to eat mosquito larvae and algae. They've doubled in size and yet, still the algae problem...
                But that's another story...

                I've stopped using the algae as top dressing because my dogs have developed a taste for it and steal it from the garden. :) Instead I just throw it in with my regular compost. I bet it's helping keep things moist and nitrogeny in there.
                @ Bulavinaka: it is hair-like. Thanks for the tip of not letting it mat up. I've been conscious of "sprinkling" it evenly into the compost bin.