I've kept mine in for a while now with no sign of issue on blade or in tank. I was removing after each use when I first started, but, then thought about constantly exposing to air and water and going back and forth. Thought it would be better to keep fully submerged. Just my thoughts and opinion. It's been 3-4 months and still the same blade with no risk of scratch. Then again, it was a new tank, so not really getting into corraline too much.