General Cycle question, and frag, Lighting question.

Would it be at all beneficial to take a medium sized rock and a very small amount of sand out of my cycled tank and but it in the filter?
This will only be for a month maybe a little longer.

 

IMO that would be far more beneficial than just using used water. Though there is bacteria in the water column, the vast majority of beneficial stuff prefers to be on a substrate. Each kind requires a specific environment and sand and LR provide variability due to microzonation (mostly concerning oxygen levels).