Na no siporax at all. made sure I didn't have any signs of that in my tank. I have given the tank 100 litre water change over 2 days cleaning 60% of the sand as I had elevated sulphur and had noticed a few black patches of sand in some calm areas at the back so have remove this and given it a good clean in fresh RO water. new pod arrived so now have 4 stages on RO unit. goes Cation 7tds, Anion 1 tds, Mixed Bed 0 tds, Mixed Bed 0 tds, I would hope now I am removing a lot of the silicate from the RO water. fingers crossed. thanks for all you help and info though guys.