Yes I use this. Well, I used to use the 'basic' pro reef, but then moved recently to the pro reef bio actif. As this contains additonal bacteria and carbon dosing. Yes it is expensive but I find it mixed to the full volume as advertised unlike some others. Plus it mixes well with little residue. Another reason I selected this salt is due to the parameters. These are closer to how I run my tank. So it is important that you select a salt that meets your parameter needs. With the actif I get carbon dosing included so I can be sure I dont overdose. Note if you do use the actif you may find there is some cloudiness with the actif salt mix but I read this is the biological action, and it clears up in the tank. Clumping.... hmmm do you mix with chilled RO water? Clumping can occur if water is too warm. Hope this helps. Sent from Singapore Reef Club mobile app