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Green water in pond

ColinAColinA Posts: 392
in Problem solving
Has any body got a home made cure for green pond water, I had the same problem for the last couple of years, I have got the KH up to 9 by adding baking soda again, this worked well last year but not this I have used preparatory so called cures to no avail the algae clumps up ok sinks and the water stays just as green. 
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  • Pete.8Pete.8 Posts: 11,340
    The stop the green water you need to starve the algae which is causing it.
    To starve it, add oxygenating plants - not plants in baskets etc - but the type you just chuck into the water available from any aquatic store.
    They will grow fast now it's warming up and will outcompete the algae and starve it.

    I don't think adding baking soda is the way to go.
    What is the idea behind that?

    Billericay - Essex

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • ColinAColinA Posts: 392
    I was recommended baking soda by a local aquatics centre to raise the KH hardness,
    at least half the pond surface is covered by various plants including Canadian pond weed
  • bédébédé Posts: 3,095
    edited June 2023
    I don't do much.  Everything in balance (touch wood,  and I'm leaving it that way).  I don't measure pH, but 9 seems very high, seeing that the scale is logarithmic.

    The cause of green water is too much food for algae.  Algae wake up first in the spring, and can dominate.  Cure, patience.  Add less food (for fish?).  Get other things to eat the algae food; namely oxygenators.  Have less light, ie. floating plants - water lilies.  Remove anything rotten.

    I do get filimentaceous algae early season, but this keeps the water clear.  My cure for that is simply pull in out in handfulls.

    So no simple "cure".  Just prevention.
     location: Surrey Hills, England, ex-woodland acidic sand.
    "Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
  • ColinAColinA Posts: 392
    I have Canadian pondweed and have covered the surface in bright weather with a black sheet all to no avail
  • bédébédé Posts: 3,095
    edited June 2023
    Canadian pond weed should help, but brings its own problems.

    I can only suggest that you sort out the more basic causes and just give it time.

    KH is hardness, ie Calcium.  I don't recognise the units.  My pond works well with tapwatr top ups.  No problem with chlorine, no problem with calcium (quite hard Surrey water).
     location: Surrey Hills, England, ex-woodland acidic sand.
    "Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
  • bertrand-mabelbertrand-mabel Posts: 2,697
    In the past we have used barley straw in a net bag and put in the pond. When we couldn't get barley straw we used long grass cut from the orchard. It did work.
  • Pete.8Pete.8 Posts: 11,340
    Like bédé, at the moment I'm removing the filamentous algae (the bright green bubbly stuff) by lifting it out with my fingers and leaving it on the side of the pond.
    The water is also greenish atm.
    I use hornwort as the main oxygenator and that's just starting to appear.
    It'll soon start growing fast and the water will clear.

    To keep the sides of the pond clear add some ordinary pond snails. I was surprised at what a good job they do. 

    Billericay - Essex

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • LynLyn Posts: 23,190
    Don’t cover it with a black sheet,  ponds do best in full sun. 
    I use hornwort,  but it’s covered with water Lily leaves,  plants just dropped in,  not in pots.  Some other plant covers it early,  water hyacinth I think it called. 
    Gardening on the wild, windy west side of Dartmoor. 

  • blacksweetrollsblacksweetrolls Posts: 16
    It's interesting that you say the baking soda worked last year but isn't this time. Have you tried adding activated charcoal to the water? That might help clear it up. It's also possible that you just need to give the pond time to balance out naturally. Good luck!
  • FairygirlFairygirl Posts: 55,117
    This is where the watercress chucked in can also help. It feeds on the nutrients the algaes need to thrive.
    Water hawthorn is also good for surface cover @Lyn, but it's a bit later and prefers a cooler site. It self seeds though.
    It can take a while to balance out, depending on various factors, but most people have to twiddle a stick at this time of year, or earlier, as the water warms up.  :)
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
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