Almost all fish die in pond, how is this possible?

[LinuxRevolution]

We had about 13 goldfish in a pond, then when I got home one day, they were all dead except for one which I saved.

WHY DID THEY DIE???

There was a plant, a Kangaroo Apple (Australian native) which seemed to be infected and the leaves were dropping into the pond for a few days.It didn't seem to affect the fish, but it obviously has. What other way could they have died?

Do you think it was the plant? It had rained heavily today, so poisons could have leached off the plant.

Also, what do I do now? I think the water is now unfit for fish and will have to empty it.
Any info at all would be appreciated. I really feel bad for these fish as I spent a lot of time fixing up the pond and looking after them and it sucks that they suddenly died.

PLEASE HELP!!!

 

[koikeepr]

The typical reason ALL the fish die like that is poor water quality. Did you do frequent (weekly) partial water changes? What are the numbers on your water parameters?

 

[j.w]

I found this on the net:

Kangaroo Apple (Solanum aviculare)
The name of this plant is Poroporo in New Zealand. The common name Kangaroo Apple is from Australia. It is a soft-wooded shrub, native to New Zealand and the east coast of Australia. Its hermaphroditic (having both male and female organs) flowers are white, mauve to blue-violet, 25-40 mm wide, and are followed by poisonous berries 10-15 mm wide, orange-red to scarlet. The leaves and unripe fruits of Poroporo contain the toxic alkaloid
solasidine. It is also cultivated in Russia and Hungary for the solasidine which is extracted and used as a base material for the production of steroid contraceptives.

 

[DrDave]

If there is any chance of poison from the tree, then I would drain and rinse it out before refilling. The poison would be diluted enough as long as you don't allow it to happen again.
Remove the tree or move the pond might be on your list of things to think about.