Someone already suggested ducks, geese, turtles, etc. -- but based on the
size of your water garden, any water that came in with new plants might have
been a source.

Just a guess,

Anne


"jw 111" wrote in message
...
hi, we have a water tank in the garden in london, england 2' (feet) by
4' x 2' high that overflows into a smaller water tank 1.5' x 2' by 1'5
high. in the larger tank are two goldfish and in the smaller tank just
some water plants.

we have recently found some extremely tiny fish in the small tank. they
are very similar to ones in a stream that runs about 100 yards from our
house.

since we did not put them in; the question is how could they have have
possibly got in there?