I just set up my tank. I used my sand from another tank that had been sitting dry for 6 months. I cleaned the sand really good. I put charcoal in the HOB filter and dropped a bag of charcoal in the tank 2 days ago. I don't get it the last time this happened was because I used new sand but it cleared up in 2 days. I'm on my 4th day and no change. ? Thank you. 

