Graham - thanks! I have a large air pump and 2 stones, but believed that
adding oxygen to the water would only promote algae growth (The "enzyme"
solution is described as "enzymes using all the oxygen, thus depriving
blanketweed of it, and therefore markedly cutting its growth"). So, except
for the "hospital" barrel, the air-pump has not been used.

Like you, I've a computerised de-ioniser on the pond, and another in the
house. As far as I can see, neither work - the electric kettle still
"chalks" up. I have a fixed magnet - I'll see if it makes a difference -
thanks for that tip.

The I-Tronic blanket weed solution is expensive, and clearly works by adding
copper in minute quantities (but, which copper salt is it?) I take your
point about the toxicity - ANY copper will immediately kill all molluscs
(snails) and it's clearly a very fine balance to kill blanket weed and avoid
killing fish. I'm investigating that (plus, the actual copper salt
generated - seems to me that adding a gram or two from a chemist is far
cheaper than £120 plus anode replacement. This could be acheived without
danger by removing the fish, dosing with copper, killing the blanket weed,
then draining and replacing the pond water - in theory, anyway.

I'll try the air-stone thing first, as you suggest. I'm not really keen on
adding chemicals unless they're beneficial!

Yes, you're not far from me, less than an hour's drive (which means you are
in Japanese Koi Co, Henlow, Beds, catchment area. DON'T go there for fish !

Thanks again, Len.

"Graham" wrote in message
news
I live just west of Cambridge, CAMBS so you must be fairly close!
The coil thingies are the same as the regular plumbing fixes for
preventing calcium ions from sticking to hot water systems.

They are designed to be identical in operational effect to fixed magnets,
but I suspect they tend to de-gauss objects and therefore have no effect.
Permanent magnets on the other hand DO stop calcium sticking as I've used
a Liffe one in my house for 5 years since getting rid of the old chalk
filled hot water tank, and the new one still has a shine on the inside.

I just stuck a big magnet off of an old speaker into my 4" gravity return
and haven't had a blanket weed problem since, although that might be
coincidence..

Copper is toxic to fish and plants, I'd avoid that. Also the dead weed
will then feed the new growth and you'll get twice as much.

The only useful thing I've heard is to use a bigger filter than you need
(perhaps add a trickle filter - a barrel water butt full of porous ceramic
with a few 2" perforated tubes to allow the air around) and to mix air
into the water just before it enters the filter.

Interestingly I solved a year long problem with algae in my pond by
getting a big air pump and dumping a couple of big airstones in the water
- it worked like magic, so it might help the eco-system deal with blanket
weed too..

Graham


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