I have sand in a 120 mbuna and they seem to love it. Always picking it up and moving it, just using PFS that I picked up from Wal-mart and washed really well. It has good weight so it sinks very well. After I washed I put a small HOB for about a day with floss to get any small grit out before firing up the canister filter.
I also have about 150 lbs of rock in my tank so I put in egg crate across the bottom and very little sand under where I was planning to put the rocks. So far with a python no problems.