Hi,
when it comes to most things in a reef, including Silicone Oxide, prevention is better than the cure.
Firstly, silicates are found in a natural reef and some creatures depend on them for survival so you are not looking to eradicate them entirely. However, they are not needed at very high levels so I would suggest the following:
1) Use RO or RO/DI water for all water that goes in the aquarium
2) Use Calcereous sand instead of silicate sand
That's should just about clear up your problem.
Regards,
Tom