Originally Posted by Sid Squid

Two thoughts:

1) Buy a big, bad tempered dog, and don't feed it too much, you want it to stay sharp.
If and when it tears the legs off some thieving chav filth who's trying to nick your bike, finish the scum off with the iron bar and bury them in the garden, no loss to anyone and a positive benefit to your soil as the piece of s**t will be fertilising pretty flowers for a while to come, which will be way more use than it ever will have been in (pond) life.

2) Make sure it's locked good, get a ground anchor, and put a bell on a cord from the cover, (yes really), and arrange a second sensor out of reach.

Option 2 does have some merit of course, but on balance I prefer option 1, not only will it be quite satisfying, but it can reasonably be considered a public service too, everyone's a winner.