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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# Email: gpw at ironman (dash) consulting (dot) com #
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