Sand is actually a great substrate for fish like pleco's because it doesn't trap waste in it like gravel does and so generally speaking it is an easier substrate to maintain and keep clean.
The only drawback is that if your gibby is very large, it might kick sand into the filter depending on what type of filter you have, but as long as you raise the bottom of the filter a couple of inches above the sand, this should not be a problem even with the largest and most active gibbys.
I have sand in all of my tanks and all of my tanks have at least one type of pleco in them, i would totally advise sand over gravel as a substrate for pleco tanks having had both gravel and sand and found that sand is so much easier to keep clean .
There are different types of sand you can use, the most common are either silica/blasting sand or childrens playsand- you should wash the sand out before you put it into the tank though, as otherwise all the dust in it will make the water appear cloudy for a while.
Do not use building sand though as this contains all kinds of nasty toxic setting agents and stuff and will kill your fish. Also avoid coral/marine sand as this will change the ph of your tank.
Very true,had to remove my sand.My large Pleco liked to burrow when he stoped swimming,sending large clouds of sand grinding into my impeller.If you have a W/D then go for it.IMO a large one will kill your power filter.HOB or Canister.