I've posted this before, but it's worth repeating, if you put ground limestone around the pool the worms run the other way.

According to the Ag Extension group from PSU, worms do not like soil with a high pH. I do a strip about 15 feet wide all around, costs about $3.00 a bag and I get 6 bags from the local feed mill to do the area. It works for me, and it doesn't hurt the grass.

BTW I took the corner loose from my pool cover today and dropped a sump pump in to circulate and test. There was only about 3" ice on the surface but I could see around the edges that there are NO WORMS again this year YEA So I don't have to do any CPR