They were embracing in ecstacy the last night of their life.
The circumstances of their death is a mystery to me -- mostly.
Here are the facts as I know them.

On April 22, 2006, I decided to clean out the fish pond, an
annual occurrence. This year, there was one koi and one
goldfish as well as several water lilies. The rest of the life
in the pond was algae, water fleas, red worms, etc. The night
of the 21st, I heard the singing of toads, but on the morning
of the 22nd there was no evidence of their romantic interlude.

The cleanup procedure proceeded like this. I filled an aquarium
with water from the pond and installed an aerator and turned it
on. I started the pump, pumping water out of the pond until it
was just a few inches deep. I caught the fish and put them in
the aquarium. I removed the pots of water lilies and placed them
in the shade. Then I pumped out as much of the rest of the water
as I could. After that, I dumped the remaining water out by lifting
the plastic pond.

I washed out the pond with a jet spray from a hose, then left the
black plastic pond sitting in the bright sun to cook the algae.
When it was good and cooked, I took a scouring pad to the plastic
to remove all the algae. After removing all the algae (no chemicals
were used), I sprayed it out again as well as I could. Then I
installed the plastic liner back into the hole in the ground.

I placed the water lilies back into the pond after removing all
dead matter and algae from them. Meanwhile, I kept an eye on the fish,
and they seemed to be keeping an eye on me as we wathced each
other through a pane of glass, something unusual for pond fish.
To keep the fish from jumping out (they normally don't jump,
but better to be safe than sorry) I placed two heavy rocks over
the aquarium leaving a crack about a quarter inch or less free.

I refilled the pond by sprinkling water into it. I also had the
fountain on. The idea was to create as much of an opportunity as
possible for the city chemicals to evaporate from the water. My
plan was to put the fish back into the pond the following day,
after treating the water.

For some reason, at about 4 in the morning, the thought crossed my
mind that the fish might be vulnerable to possums or racoons. So I
went out to check on them. Mysteriously, the koi was missing, but
the goldfish was still in the aquarium. The two rocks were still
securely covering the aquarium, so I can't see how the koi escaped.
Thinking that a racoon or something got the koi, I decided to move
the goldfish to the pond. That's when I noticed the pairs of toads
courting in the pond. There were three pairs in amorous embrace.

Wondering where the koi was, I got a flashlight and conducted a
thorough search of the area. It was not in the aquarium, a 10 gallon
aquarium where it would have been easy to spot (the koi was about
10 inches long). The pond was freshly cleaned and crystal clear. I
searched it thoroughly but did not see the koi there either. I did
see the goldfish (about 4 inches long) several times while searching
for the koi. I searched the grass around the area and didn't see
anything. I searched the water of the aquarium thinking that if a
beast had done the dirty deed it would have left some evidence.
There was no blood and no stray hairs. I saw no footprints, although
there really wasn't a good place for them.

Mysteriously, though, the aerator was not running. This could have
allowed the water to get stagnant, prompting the fish to jump, but
there's no way either fish would have been able to get past the rocks.
I followed the cord of the aerator back to the plugin, and it was
still plugged in, albeit loosely. I plugged it in more securely, but
the pump was out.

It was still the wee hours of the morning, so I decided to continue
my investigation in the morning.

The next day (today) I went out to the pond to continue my
investigation, and I saw the koi floating on its side in the
pond. How it got into the pond is a complete mystery. How it
died is also a mystery. Then I noticed the dead toads. Two had
sunk to the bottom of the pond, the rest were floating on the surface.
I'm thinking now that chloramine is what killed the koi and the
toads, although I didn't think adult toads would be vulnerable
to chloramine since they like living in flowerbeds moistened by
city water.

I fished them out and placed them on the ground, remarkably life-like.
For some reason, I decided to take a few pictures. Here's one. I didn't
arrange them for the picture. That is just the way they wound up when I
fished them out of the pond.

I feel like I've been plunged into the Twilight Zone.

Oh, by the way, the goldfish is still thriving in the pond.