I read that these - nasty - critters eat algae. Is your pool a bit greenish? We can help with that. To reinforce what Watermom said, you'll need a good (k-2006) testkit to start.

BTW -I had a few of these in my pool last year - a year I didn't close because of a big autumn storm (Sandy) followed immediately by snow - by spring I had a swamp (with fauna) to clean. The bugs were gone after a week at shock level FC. Kill the food - kill the bugs.

Good Luck