I have pool filter sand in all my tanks (26 total so far) and I love it. It is just crushed quartz - doesn't bother your water parameters at all. I have tried a little play sand - too fine in my opinion and too much comes out w/the python. If you have bright lights - you will probably have algae problems w/the sand. I have a small angelfish hatchery and most of my lighting comes from lights that I have hanging over top of the tanks. I have seen some beautiful tanks w/sand and a lot of plants - if you have plants that will out compete the algae for food you will probably be OK. the other thing you have to watch out for is anaerobic pockets developing in the sand. You have to keep the sand from compacting down too much or it will go anaerobic. I use a python to move it around on a fairly regular basis - no problems so far. The other thing - if you do not do regular water changes w/substrate cleaning you will have poo everywhere. Sand does not hide the poo like gravel can - it all sits on top - you need to clean it off once a week or so.
HTH,