When the filter was first set up the flow rate was too fast, a regulator valve was added.
.25mm sand on the top 4 inches; .45 mm sand bottom; pea gravel bottom 4 inches; carbon granule filter on output; 3 weeks running after extended freeze. As of today March 7: 24 degrees F.
March 6 2012: flow volume: 37.5 litres per hour ; flow rate: .140 meters per hour