In article ,
says...

kay;951274 Wrote:
Why?
And how often?

It's often difficult to get a natural balance in a small pond, the
effect of sunlight will turn it green and may even make it go "soupy" so
you won't see your tadpoles.

[image: http://img534.imageshack.us/img534/9927/pic002a.jpg]

An occasional trickle change will resolve this.

But it has to be just that, nature doesn't like rapid changes in
conditions.

I do ours a couple of times in the summer. I also clear out all the dead
vegetation before spring (it will seem that every leaf that falls in the
garden will likely end up in your pond) as it's likely to be acidic.
Frogs can absorb toxins through their skin.

I put a light net over the pond for a month or so in Autumn to keep
falling leaves out.

Janet