try and either take the sand out and wash it before putting it back in. which i dont think is possible. But that happens the first day or 2 let it filter through and check your filter every day and rinse it out so the sand dosent get clogged
You can siphon it out into a bucket and then wash it outside. Use a garden hose to keep it stirred up in the bucket, but do not use so much pressure as to cause the sand to flow out of the bucket. The silt will suspend and you can dump that out. When the sand stops producing silt, then it is ready to go back into the tank. You can use a tarp to hold your sand if you can not find enough buckets.
i wouldent recoomend putting chemiclas in the tank, it will take time and will eventually settle but then if the sand is disturbed it will be cloudy again, sounds like a 100% waterchange to me, ALWAYS RINSER UR SH*T!!!!!