Fishman, my play sand took a long time to completely settle. I thought I had gotten most of the dust out, but I was limited to using the kitchen sink sprayer to wash the sand and I wasn't very patient when doing it. I put the fish in afte a couple of days, but it took about a week for all the dust to settle or get filtered out. If your tank is freshwater, I'd think about replacing the sand again. Not 100% sure, but I would expect live sand to be aragonite based, which will raise your ph above where most freshwater fish are comfortable. Conversely, if the tank is saltwater, I'm not sure the play sand will buffer the ph level in the tank enough.