I put a bag of sand into my 30g. the bag recommended I rinse, but that it was not required. So...I didn't. I figured it had all these trace elements it said it had that I wouldn't want to rinse out. well 2 days later its still cloudy. I'm not worried if it just needs more time as I'm in no rush to finish this project, but I just wonder if it will clear or if I need to start doing water changes.