Have a small pond, 750 gallons, linered, had it going almost 1 year.

Is it normal to have worms (look like common earth worms) and some white
thingies that look a bit like snails without the shells (or grubs or
something, about an inch or so long) in one's pond?

I am not infested, but there are some.

(I've even seen a goldfish try to eat one of the white thingies, hangs out
the mouth an inch or so.)

Curious...