Mustard algae (also known as yellow algae) is commonly mistaken for dirt at the bottom of the pool. This form of algae normally grows on shady areas of the pool and killing it requires an extra chemical such as Yellow Out in addition to chlorine.
If I ever have a pool I'm totally going to get these! The Ocean Art Light-up Jellies from Swim Ways are eerily life-sized jellyfish decorations for swimming pools. Each light-up jellyfish has LEDs inside and glow as they float across the pool.
How to Eliminate and Prevent Green Algae in a Swimming Pool. Green water or floating algae are common problems in swimming pools. Treatment can take multiple chemicals and several days of waiting if the algae has had time to build up.