I had a pretty bad case of dinos, I removed all corals and clams, blasted the entire tank including the sand bed (not a DSB) to suspend as much detritus as possible, and did 20-30% water changes at the same time to get as much crud out as possible. Did this I think 3 times in a weeks period, changed the lighting to my Chaeto to PC's and increased it's photo period to abt 14hrs, Dinos completley gone in 2 or 3 weeks. The source of silicates in sand and it's effect on dino growth is one of those debated issues. It is true that the dinos skeletons are primarily silica, however as I understand they still require the normal nutrients to grow. Phosphate and nitrates reading zero are misleading as they are no doubt being consumed as they are produced. Consider a common occur. Red Slime, treated with remover, followed by hair algae and dinos. all because of some nutrient in the tank, one gone, another replaces until the nutrients are removed. Skimming and nutrient export are probably the best bet IMO and it worked for me. it may or may not be safe to actually disturb the sand bed, definatley a no-no if you have a DSB, but I did do it without adverse effect (2"sand bed)
