I have a lovely little pond that I created in my London garden last year. I filled it with a variety of wild plants and weeds, and also frog and toadspawn from my mum's pond - they would never have survived there because they can't get out of it, and I am in a part of London where there is no way a frog would have been able to get to my pond to spawn itself.

Anyway, I had hundreds of froglets all over my garden (I kept them fed with dog food), and I was looking forward to another bumper year. Knowing that they take a couple of years to reach maturity, I got a load more spawn, but noticed that the nucleuses of some were like worms rather than spherical.

I thought nothing of this, until I noticed that they moved to the edge of the spawn and every single nucleus was gone. It turns out that they were all leeches. Not just that, I set up a leech trap in the pond, and hauled out so many leeches, it is clear that I have been breeding them in vast numbers over the past year.

I realise that I won't get any froglets this year, but my concern is now next year, when my frogs come back to the pond to try to breed. I have no fish in the pond, and can't find any information about what predates on leeches - especially that doesn't predate on tadpoles!

What can I do to balance the ecology of my pond better? What can I put in there to eat at least some of the leeches? Would sticklebacks do it? I know a stream where there always used to be some.

I would like my pond to be friendly to a wide variety of wildlife, but at the moment it appears to be a danger to my favourite visitors...