After a decade of using IO/RC, and fussing about having to clean the brown film from my mixing vats, I switched to Tropic Marin Pro Reef. I have a much larger mixing tank now, and dreaded the thought of having to lug it out of my basement, scrub it, and set it back up. The BRS investigates sold me on TM/PR. I can now mix up enough saltwater for three water changes, and not have to worry about parameter swings in storage, but most of all... it mixes CLEAN with no residue. Yeah, I'll pay more for those bonus features.