IF YOUR UNIT IS SET RIGHT IT WILL SHOW PVC WITH OR WITHOUT ALGAE,I PUT OUT MANY THIS YEAR AND THEN COME BACK THAT DAY TO CHECK ON HOW WELL I COULD SEE IT,YOU HAVE TO REMEMBER IT IS NOT AS BIG AS A TREE(AT LEASE NOT MINE) SO IT IS GOING TO LOOK SMALLER THAN ONE WOULD EXPECT TILL YOU START REALIZING HOW SMALL A OBJECT LOOK ON DI AND EVEN SMALLER ON SI WITH A LONGER DISTANT AND THEN DOUBLE IF USING BOTH SIDES