Hello,
I have a garden pond in the UK, about 20 ft x 15 ft. The pond has no
pump, but lots of plants (and blanket weed)
but the water is generally v clear & seems healthy.

A few days ago, I noticed a dead goldfish floating on the surface. There
were no obvious signs of injury / disease.

Now, today, one of the larger fish is rather 'dopey', and has pronounced
white blotches around it's face. I managed to scoop it up quite easily &
you'll see from photo linked from below that it also has small, dark spots
on its side.

http://www.pbase.com/image/15963257

Neither the original, dead fish, or any of the others now in the pond
displayed any of these signs.

Am I worrying unnecessarily, or does it look like there's something nasty
going on?

NB although I have few fish, the pond is essentially given over to frogs,
dragonflies etc so I'm reluctant to treat the water with anything which
might adversely affect the wildlife

I'd be grateful for any advice - thanks

Sarah