Years ago this was destined to be the blanket weed FAQ but Cormaic left
before it was created:
Algae, which includes blanket weed, thrives on nutrients, sunlight and
carbon dioxide in pond water. This is why blanket weed topics always
crop up on urg at the start of summer. Sunlight levels increase, pond
water starts to turn green and blanket weed grows.
For starters -
Are you sure that nutrients (compost, growmore, miracle grow, dead
vegetation, plain old soil etc) are not being washed off your garden
and into the pond when it rains?
Are you sure you are not overfeeding your fish and that the extra food
is rotting to provide blanket weed food?
Is your pond is a new one? Don't keep filling it up with 'new' water to
try to clear it because if you do, you will just set yourself back to
square one every time as most tap water contains levels of Nitrate from
farmland runoff thus increasing your problem.
Take heart from the fact that it can take three or four years for
the water in a new wildlife type pond to stabilise into a well
balanced state.
Does the pond have a liner or is it a manmade 'natural' one ie a big
hole in clay ground? Nutrients may be more of a problem in a natural
pond than in a lined one - but don't quote me on that.
Blanket weed isn't killed by your pond filter.
Blanket weed will happily clog up your filter.
In fact, if your filter is a biological one, it will actually convert
toxic Ammonia waste from your fish into less toxic Nitrates again
increasing your weed problem.
To make the blanket weed disappear, find a way of reducing the
sunlight and nutrient levels in your pond and increasing the oxygen
level.
Our local pond expert says:
"Don't work against mother nature, try to work with her".
The most natural way to remove blanket weed, as it starts to grow in
early summer, is to encourage lots of tadpoles. Among other things,
they feed on blanket weed. However if you keep fish in your pond the
tadpoles will be a welcome food for them.
Here are some suggestions
=========================
Reducing sunlight
-----------------
Reducing the sunlight entering the pond is usually achieved by making
sure the surface is half covered with leaves of lilies or other
surface hugging plants such as frog bit and aponogeton.
Some urglers have even tried:
- Azolla (fairy moss) - fast growing and can be scooped off the
surface without harming the pond creatures.
- Covering the pond with a big sheet - can be placed over the pond
when sunlight at its brightest.
Reducing Nutrients
------------------
Reducing the nutrients is achieved by continually removing the blanket
weed. That is, as the blanket weed grows it absorbs nutrients
therefore the more you remove from the pond the more nutrients are
removed.
To catch your blanket weed, you can use a tuning fork shaped
stick and twirl the blanket weed round it. You can use a plain
straight stick if you want and use the same circular action as a
candy floss catcher.
Just be careful that no little pond creatures are caught in the
weed as you remove it. In fact, leave it at the side of the pond for
a couple of days so any that are caught can crawl back into the pond.
It has also been suggested that growing water cress has the same
effect. It grows quickly therefore absorbs nutrients so that the
more you remove, the more nutrients are removed. The same can be
said for any aquatic plant, but water cress seems to be the fastest
grower therefore the fastest nutrient absorber.
***Warning*** do not eat any watercress grown in a pond because it
could give you Liver Flukes.***
Increasing Oxygen
-----------------
Well, obviously, you chuck in some oxygenating water plants.
It is amazing to watch the streams of tiny bubbles rising from
these plants when the sun shines on them!
Some things other people have tried
===================================
Barley Straw
------------
Barley straw works very well it just takes a little time. It *has*
to be barley straw and not any other kind. I have used this method
for years successfully.
[OldMolly]
I also use barley straw. Research papers that I have read suggest that
the barley straw works best when it is placed in front of moving water
and hence giving the naturally released chemical, that I believe
prevents the weed growing rather than killing it off, an opportunity
of dispersing throughout the pond.
[AndyP]
The reason that the Barley Straw works is AFIAK it absorbs the excess
nitrogen in the pond that the algae feed on. Yes it must be organic,
or bought from an aquatic shop, as the chemicals sprayed on to it by
farmers will kill the wildlife in the pond. Growing it yourself is
one good answer, if you have the space.
[Mike]
Chemical Solutions
------------------
From what I remember of a chemical solution to our small pond years
and years ago, a chemical solution to your size of pond is going
to be expensive.
[Jane Ransom]
I cannot vouch for CLAROSAN as I have never heard of it. But with
respect to harming lilies & other plants most of the other chemical
remedies do. I would check what the manufacturer has to say about it
before use.
Chemical treatments can stunt growth/or even kill plants altogether,
but usually just prevent lilies flowering for 2-3 seasons and if you
think that is OK just remember when you stop treating the water, the
blanket weed WILL come back.
Remove the nitrates/light in your pond or get a couple of million
tadpoles ;-) Tadpoles are the best bet. They will chomp away & keep
it away until the plants have time to grow.
[Andy]
If you use chemicals to get rid of blanket weed, you must make sure
to get rid of the dead weed from the bottom of the pond, or it will
clog your pump and possibly affect the water even worse than the
weed did.
[June Hughes]
I once tried some that said it didn't harm plants, but at the
recommended dose, it most definitely did, and quite badly. And after
a few months the weed came back. Cant remember the make though.
[TumbleWeed]
Funny you should mention that, this year, despite it being sunny,
we have had little trouble with Blanket Weed which normally blocks
filters, pumps etc. Three things may have affected this:
The first is that we have let our Watercress grow rampant before
removing it (and the nutrients it fed on) to the compost heap.
The second is the use of "Pond Tonic Salt" at the recommended dose
(originally introduced because of a parasitic bloom which was affecting
our fish) and
The third is that we have not changed the water in our pond as much
as normal just increased the flow rate of our filters a touch to keep
the water sweet (it's a 3,000gal Koi pond so a lot of waste matter).
[Bob Hobden]
Yes there are chemical products which remove blanket weed but,
having killed off the b'weed, the weed decomposes and eats up what
oxygen is in the water. So, the usual recommendation is to remove as
much of the weed by hand, before one treats the water. Yes, this can
be a big job. I have seen boats being used to trawl the stuff up.
However, you asked what the products might be. One was called 'Algofin
Plus'. No doubt you can buy it in larger more economic quantities but,
250ml to treat 5,000 litres used to cost £5. - No cheap option !!!
Another product was called 'Algizin P'.
I found that patience (nature is a great healer) and adding no more
tap water seems to pay off.
Don't worry about the magnitude of the problem. Just think how
satisfying it will be when you succeed. ;-))
[ned]
But always bear in mind
=======================
The root causes of blanket weed are:
-> nutrients
-> sunlight
-> carbon dioxide
in the pond water.
Get rid of them and your blanket weed D I E S :)))
--
Flossie