sand also compacts over time .. so you'll have to use something like a fork to poke it once in a while so stagnant air bubbles don't form in the sand and turn into bad gasses for your tank .. and since it does compact .. it'll be very hard to grow any plants in the sand since the roots of live plants will have a lot of difficulty growing when it's compacted that is if you decide to put any live plants in your tank ..
also sammy ... my bf's betta loves to dig holes in it (only in the corners for some reason) .. and usually gets sand all over his tail fins
.. and i worry so much that he's gonna get sand stuck some place bad .. like his labyrinth .. but so far so good =)
i've had all sorts of substrate .. glass beads (including marbles and decorative glass shells and stars) .. real fine sand (the kind you would see on those white sandy beaches .. and when it's dry if you sneeze it'll float away and kinda looks like it's melting when it touches water) .. regular AQ gravel .. fine "sand" gravel (i do not recommend this kind .. looks like sand .. packaging also said sand it really isn't .. cus behaves like gravel that was crushed into a smaller grain and floats on the surface when cleaning .. got it at petco .. it's a bad bad substrate) .. out of everything that i use .. i like fine sand the most .. it's a pain in the rear-end to clean for initial use .. but maintenance is a lot easier then gravel .. and if you have a hard time not sucking up the sand when using a gravel siphon .. what u do is detach the actual siphon handle and just use the connector tube .. then keep it 1-2 inches away from the top layer of sand .. and that should pick up any debris that lays on the surface of the sand without agitating the sand if that makes sense =D
it all depends on what your planning for your tank
*side note* if your planning on doing a dual substrate with gravel and sand .. so you can plant live plants and keep the sand look .. make sure to plant your plants in the gravel first before laying the sand .. that way when you add water .. the sand doesn't fill in all the crevices of the gravel which will then block roots to grow =)
last note .. i also recommend using this method (youtube link below) to clean the sand for initial use .. BUT .. do not do it like this guy in his tank .. i would do it in a bucket .. then rinse it a few extra times to get rid of any excess cloudyness that could come with using sand (i rinsed about 50 times after .. then let it stand over night .. and rinsed it again about 20 times with warm water cus i'm paranoid .. before scooping it into my tank .. the bottle really collects a lot of the initial debris and particles that comes off of new sand