What's wrong with my water?

I've got a big galvanised header tank at the bottom of the garden fixed up
to take rain water from the roof of a biggish greenhouse. last year I
thought it would be a great idea to introduce a couple of goldfish and a few
plants. Well, the plants did fine, but after a couple of days the fish went
crazy and darted around all over the place and rapidly became ex-goldfish.
Clearly the water is very soft but a lot of other little critters seem to be
ok; pond skaters and even a few frog tadpoles so the water can't be too
toxic. Any ideas anyone? i won't risk any more fish until I have good
understanding of what's goung on.
Dave

To a certain extent you have said it yourself "soft water" which means
acidic; if there are dilute acids then likely to get zinc sulphate, zinc
chloride etc etc in the water; depending upon what acids are present in the
rain water.
Zinc sulphate damages trout gills therefore I assume the same holds true for
carp. Haven't even bothered to go so far as checking toxicology of other
compounds of zinc.
Presume the tank was used in a domestic situation once in which case I would
have thought that it has a deposition of calcium compounds which would tend
to neutralise the acids until such time that it was used up.
You could try a buffering agent; oyster shells and calcium carbonate based
rock spring to mind together with a liner: then that variable is resolved.
The other major variable is what was the health of the fish you introduced;
as you will appreciate any one's guess.
Best of luck next time.
Roddy




"Dave" <mr_mojo_risin_ DeleteThis @hotmail.com> wrote in message
news:1056818006.41477.0@dyke.uk.clara.net...
> I've got a big galvanised header tank at the bottom of the garden fixed up
> to take rain water from the roof of a biggish greenhouse. last year I
> thought it would be a great idea to introduce a couple of goldfish and a
few
> plants. Well, the plants did fine, but after a couple of days the fish
went
> crazy and darted around all over the place and rapidly became ex-goldfish.
> Clearly the water is very soft but a lot of other little critters seem to
be
> ok; pond skaters and even a few frog tadpoles so the water can't be too
> toxic. Any ideas anyone? i won't risk any more fish until I have good
> understanding of what's goung on.
> Dave
>
>