Ah, didn't see this till after I posted the other thread!
I'd say sand as food/waste can tend to fall in between the gravel/pebble substrate and can eventually have a water quality problem.
You can get bags of playsand from Bunnings, Mitre 10, Palmers, Garden Centres or Landscaping/Hardware stores for about $8=$12 (varies) for 25kg bag.
Do you have an undergravel filter or internal filter, and did you cycle your tank?
See:
http://www.caudata.org/cc/articles/cyclingEDK.shtml
If you don't have an UG filter, and you still wish to keep gravel, here's a thread, posted by Jennewt, for "permanent sand/gravel"
http://www.caudata.org/forum/messages/793/77098.html?1170154180
If you don't already have one invest in a turkey baster, from $2 shop, they are handy cleaning tools to suck up uneaten/regurgitated food/waste/poo! We cut the tip of it so it's easier to suck up waste.
