We recently lost some goldfish to the local heron. We came up with the idea
of buying a thickish plastic netting (with a big mesh about 6.5cm [3 ins]
that is used to fix climbing plants to a wall) and laying this netting just
below the surface of the pond so that it did not look too conspicous.

The other day out of the two fish in the pond we found one fish missing and
the other laying on the lawn nearby. We are wondering If it was the heron
again? It is the only culprit we can think of here [london, u.k.]. We
thought that the netting would have been too worrying for the heron, as we
have been told that even some fishing line placed around the edge of a pond
puts it in fear of a trap.

The main part of this question is that there are minute black fish still in
the pond, which must be baby goldfish. There is also a frog (or is it a
toad we dont know how to tell) in the pond. Are these very tiny fish in
danger of being eaten by the frog or anything else?
If so then we would bring them indoors to a tank. Thanks for any advice.