Okay this is interesting, i did the rock test. I watched this BRS video: They soaked a 1kg piece of Pukani, fiji, tonga and reef saver rock then weighed them again once they were saturated to measure how much water they held and in turn how much surface area and internal pore structures each rock would have. The results were: Pukani held 380grams of water Fiji 210grams Tonga 90grams Reef Saver 60grams I tested two pieces of Real Reef Rock today that had been soaking for 7 hours. The first piece of rock was 1.033kg and it held 106grams. The second piece was 1.081kg and held 104grams of water. This puts the Real Reef Rock in the middle but is still over three times less than the Pukani and just half of the Fiji. This is good to know but at the end of the day i have 5 litres of siporax in my sump that should provide ample bacterial housing for my tank on its own before I even have to worry about the rock... I think there is something else in the live rock that the dry rock is missing and in my case its taking a long time to find it.