Yeah, my snails went from zillions this spring to "where the heck did they all go?" as the perch have been growing up. I did not realize, but glad, that perch eat snails. Good news on the leeches, not a big fan of them.
Perhaps stock some perch and a few Walleye to keep the perch in check, which I think do a lot better up North than largemouth bass. Neither perch or WE are anywhere in sight while swimming unless I sneak up on them very slowly while snorkeling.
My sister-in-law has a pond in Maine with no fish for swimming with now has leeches in it. I will send this thread her way. I did not know which fish to recommend. She is misunderstanding in thinking that it is "cruel" to trap fish in a pond, I fixed that notion for her when she saw our pond this past weekend while visiting.
