Some tips to keep the water clear when adding the sand: (I put this on a thread before.. don't remember which one or where)
1. Remove all your gravel. If the sand is in a plastic bag, submerge the bag, and cut a small slit to allow water to seep in slowly. Lay the bag on its back, and after the bag is full of water, complete the slit from the middle top of the bag to the middle bottom of the bag. Then cut along the seam at top and bottom so the bag is nothing more than a plastic sheet with a pile of sand sitting on top of it. Slowly slide the sheet out from under the pile as slowly as possible, being careful not to disturb the pile. Wait for maybe 15 minutes and begin to spread the sand throughout the bottom slowly. After about 10 minutes of that, you should be done, with just a mild haze in the water.
2. If this does cloud the water a lot, put cotton balls(and some extra carbon) in your penguins. This removes microparticles of sand (particularly silicates) quite well.
3. Put some of your gravel in media bags or a small tupperware/specimen container for additional BB, and to culture your sand bed... it'll be easier to take out when the time comes..
4. Sit back and watch your crystal-clear tank
It has worked great for me in the past. Hope it works out for you!
