In all the years of boating I have never heard anyone talk about anodes except to replace them. During my 3 year boat inspection I ask the surveyor about the condition of my anodes and do they need changed. His answer gave me the a "Da" moment when he said as long as they are intact your good to go but if they are not clean they will not do what they are supposed to do . He told me to take a wire brush to them. They are in fact a electric sacrificial contact point and if they are corroded over they aren't as effective.