Hundreds of worms when I open my NY pool

[LIswimmer]

Hi, all. I have an in-ground saltwater pool in Long Island, New York. I've had it for four seasons. The past two times I opened the pool in the spring--around Memorial Day weekend--there have been hundreds of long, white worms at the bottom of the pool. It looks like somebody made a huge pot of spaghetti and threw it into the water. Based on an internet search, I believe they might be horsehair worms, though they are thicker, shorter, and whiter than most of the photos I see online. I have no idea how they get in. I have a standard mesh winter safety cover. After vacuuming them all up, they never come back until I open the pool again the next season. I typically close the pool the first week in October.
Does anybody have any idea how to stop this from happening? Closing pool later? Opening earlier? Different cover?
Thanks!

 

[PoolStored]

Welcome to TFP!!!

This is very typical, and there is not much you can do except put a robot in and have it auto-collect.

Same happens to me here in Ohio.

The pool is a high point. It is built that way so water drains away from the pool when it rains. With heavy rain, worms seek high ground...your pool. They crawl under the mesh cover and drop in for a swim.

You can go to a tarp type pool cover with water bags, which would stop them. Given the hassle of the tarp and water bags, my preference is to deal with the worms. I just throw the robot in for a few cycles before I remove the mesh cover, worms and everything else is out. When I pull the mesh, pool is clean and clear.