I use the water from our water changes on the garden and the plants seem to
appreciate it!
And as for never doing any water changes - I wouldnt have liked to be one of
the fish in your tank/s! Partial (never full) water changes and regular
gravel vaccing are necessary otherwise you'd get a huge build up of ammonia
and nitrate over a period of months/years and I'd say that Ford sounds like
a responsible fish keeper if he does regular partial changes!
Mel.

"Alan Holmes" wrote in message
...

"BoyPete" wrote in message
...
Ford Prefect wrote:
I keep a couple of tropical fish tanks and was wondering if the waste
water after water changes would be benificial or harmful to garden
plants, seems a shame to flush 40l a week if it could be doing some
good in the garden instead.
Cheers,
Ford.
It's great for the garden. But, what are you doing with 40l changes a
week?? When I kept tropicals, I only did partial changes if water
parameters were off the normal. unnecessary changes will stress your
fish.

I kept tropical fish for years and I don't recall ever changing the water,
whole or partial.