I use SMS and while there was a minor drop in KH initially it doesn't last long. I rinsed mine thouroughly. Not sure if it matters or not it is just what I chose to do. The substrate is great but I wish i would have gotten the charcoal stuff because the red isn't very pleasing to me.

No problem with fish or shrimp health in this tank. I had a problem with some lava rock a little while back but not with my SMS.