I have never used that brand, but it doesn't sound normal. I use Instant Ocean Reef Crystals and after letting it mix with a powerhead overnight, I usually have little if any solid particles on the bottom of my mixing tub. However, I once bought a bag of Reef Crystals from a PetsMart and when I mixed it up and checked on it the next day, I had a large amount of solid white particles on the bottom. I believe the bag had been punctured at some point prior to purchase and moisture got in, causing some of the trace elements to bond together and not dissolve. I suspect that is what happened with your mix.