Kay muttered:

Lead? Is that OK in a wildlife pond?

The pond is 25 square metres, we put in 12 tench and 5 carp ‹ between they
had an estimated 100 fry last year, most of which are still alive, plus frog
spawn (all hatched now), water snails, newts, dragonfly, water boatmen,
water beetles etc etc. I don't think the 15 little bits of lead have
affected them much so far.