Blanketweed The EVIL Weed
It is fair to say, that blanketweed is the scourge of the koi
pond. Designed, constructed and maintained for their beauty, never
was a weed so out of place as in an ornamental pond - particularly
when stocked with koi. koi ponds have risen to become one of the koi
keeper's most common complaints.
The Evil Weed ... Blanket: "Heavy or dense covering". Weed: "A
herbaceous plant, not valued for use or beauty".
- Designed, constructed and maintained for their beauty, never
was a weed so out of place as in an ornamental pond -
particularly when stocked with koi.
- Blanketweed and Nishikigoi share two things in common: They
both have names that accurately describe their physical
- We don't resent blanket weed's grip on our ponds because it
poses a direct threat to the health of our koi, as in fact, it
can actually lead to improved water conditions.
- When there is a thin, beardlike covering on areas of the
pond, koi will browse and graze on the soft, lush growth.
- However, koi find it less appealing when the beard has grown
into lengths of weed several feet in length (hence its other
names such as hair or thread algae).
- Furthermore, blanketweed is beneficial to a pond in that it
will very actively take up minerals and nutrients from the pond
water (just like a vegetable filter), the only difference being
that this one is in the pond!
- So vigorous is the growth and uptake of nutrients by
blanketweed that should we find a way of confining it to a
vegetable filter, it would be our number one plant choice.
- Unfortunately, like all other weeds, blanketweed does not
know its right place and freely enters any koi pond, doing so at
its own risk, as its presence is likely to be challenged.
- Its fine filament structure and submerged position lend it
to producing a ready supply of microscopic oxygen bubbles.
- So intense may be its aerating effect that in strong
sunlight, rafts of blanketweed will rise up to the surface,
buoyed up by the mass of oxygen bubbles caught within its
- Cladophora means 'branched plant' and when viewed under the
microscope, it is possible to see the regular-branding
filaments, each of which is divided by cross walls.
- They reproduce both sexually (releasing gametes that unite
and develop into new plants), and asexually (releasing small
motile spores or simply smaller fragments that break off from
the main body).
- Algae will readily absorb nitrates and phosphates to satisfy
their need for nitrogen and phosphorous as they grow.
- As we want our ponds to be as warm as possible (to stimulate
koi health and growth), we must look at reducing sunlight and
- Erecting shading on a pergola will reduce sunlight straight
away and reduce blanketweed photosynthesis.
- Several blanketweed and algae controls work by adding dark
vegetable dyes to the pond, filtering out the sun's rays.
- Blanketweed and green water have a mutually exclusive
relationship, where ponds tend to suffer from either one or the
- Several pond treatments are available that control
blanketweed growth by locking up or removing the vital nutrients
from the pond water, starving the growth of blanketweed.
- Barley Straw Barley straw is a green method of controlling
blanketweed and green water.
blanket pond growth koi algae water
nutrients weeds sunlight control plant "green water" filter beauty
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