There Be Dragons

The dragonfly larvae in the pond are metamorphosing into dragonflies.

Here you can see an empty larval case.

We have a problem with the pond - algae.

It's caused by there being little or no shade, so the sunlight encourages the green stuff to proliferate.

Hay has convinced herself that the poo from the 3 koi is to blame and won't be told, by anyone, that 3 koi in a pond that large cannot possibly be the culprit. She's planning on emptying the pond, getting rid of the koi and then refilling it. But that won't cure the cause, which is lack of filtration. 

I keep telling her that a couple of hundred quid's worth of filtering equipment would solve the problem for good - but to no avail.