MMacro
New member
I think you are confusing "IO" (Instant Ocean) with "RC" (Instant Ocean Reef Crystals). Regular IO is the most tried-and-true salt in the business and I've never heard of any residue issues with it. RC, on the other hand, is well known to leave residue.
I am using regular IO right now for tank transfer and there is quite a bit of residue left after mixing. Mixed with fresh RODI and a sealed mixing container.