I used a solution of water and vinegar. Seen it on the web. I filled up a tub with water and checked PH, I added the vinegar until the PH dropped to 5.2. Then I let the cubes soak for 24 hours. This is to get all the lime out left over from the manufacturing process. Dont let you PH get below 5.0 in your solution. The web says it will destroy parts of the chemical make up of the rockwool.