Must be some soft metal, or you've been dosing steroids to your coralline algae.Plastic + metal
Flipper Stainless Steel Blades (2 Pack)
Two pack of stainless steel replacement blades for the Original Flipper or Flipper Float magnetic glass cleaners Compatible with the standard size Flipper or Flipper Float High-grade corrosion resistant stainless steel For glass aquariums only Replacing your blades every 3-6 months will help...www.bulkreefsupply.com