Will wrote
We have recently dug, lined and filled a pond.

We had someone round to lay some paving stones round the edge. They did
a reasonable job apart from one thing - there now seems to be quite a
lot of cement coating the liner all the way round.

I appreciate that this shouldn't have happened, but it has, and all I
want to know is a) will it poison my tadpoles and plants (I've no
immediate intention to put fish in the pond) and b) what's the best way
of removing it? I've tried wiping it out of the pond with a cloth but
this just disturbs it.

Firstly it depends how much cement has entered the pond and how big the pond
is, i.e. what proportion.
If it's like a dust coating then you can suck it out with a pond vac, if
it's large lumps then you can get most out with a net.
It won't poison your pond life as such unless it's a lot of cement per
gallonage but it will raise the pH, and a high pH is not liked by some pond
plants although most will survive at pH 7.
Might be worth obtaining a pond pH kit and measuring the water pH (also do
your tap water if you intend to flush out your pond with it).

--
Regards
Bob
"Never get so busy making a living
that you forget to make a life"