off the shelf "live sand" is so callec because its reputed to have live biological coponents to it. But as Dmatt88 said, without oxygenation and circulation, those die over time. So adding it to your tank is guaranteed to cause an amonia spike. Strait up dry aragonite gravel or sand is best to add to an active system. Rinse it well to get all the dust that can cloud the water off, then add slowly (again as Dmatt88 said) through a Pipe or tube, directly onto the existing sandbed. Mix it with a glass rod or pvc pipe. Mix slowly to avoid clouding.
Cyano is a natural part of the process of cycling. People toss around the word Cycle and mention 3-8 weeks...but everything i've seen and read says the cycle isnt complete till the tank is stable and fairly static for 6 mo. So cyano can break out for short times when changes are made to the tank, or when excess nutrients are present. Nitrate/phosphate are the 2 most common, but there are others, ie Silicates, excess feeding etc. Unless the cyano becomes a nusance(ie covering corals), its easiest just to vaccuum it off and wait to see if it comes back. By vaccuuming it off, you remove not only the cyano, but the nutrients it would break down into naturally, from the system. unless the cyano persists longer than a couple weeks, i wouldnt worry too much. If it does, do a couple 25% water changes, made with RO/DI water, cut back on lighting schedule to 7hrs a day or less, and monitor feeding. Almost without fail, every time i rearrange my live rock(big changes to the tank), i get a cyano outbreak for a few days.
