Mmmm... Håller i grund med med basserar det på denna artikel. http://www.wetwebmedia.com/ca/volume_6/volume_6_3/refugiums.html "The minimal flow rate is a turnover of 5 times the volume of the refugium, and this would be suitable for refugia with DSBs. For refugia with Chaetomorpha, faster flow rates are required, turnover rates of 10 times the volume of the refugium being appropriate."