Skimmers and Auto Feeders for Koi Ponds 1. Skimmers: Skimmers are essential components of a koi pond filtration system. They are designed to remove debris such as leaves, twigs, insects, and other surface contaminants from the water's surface before they sink to the bottom of the pond. Here's why skimmers are a good investment for koi ponds: Water Quality Improvement: Skimmers help maintain optimal water quality by preventing organic matter from decaying in the pond, which could lead to algae blooms and foul odors. Cleaner water promotes the health and well-being of koi fish.