one thing for sure rinse, rinse, rinse, rinse it should run clear and it will take a little while.
keep a cup or two of gravel and put it in the end of a clean nylon or something and keep it in for a week. this would be a bad time to change the filter media too.
downsides to sand? without plants and with a deep enough bed theres alot like hydrogen sulfate i think. in anaerobic pockets. the key if you got these would be not stirring deep, like more than a 1/2 inch at every water change. i feel maintenance is easier, just wave the wand above the sand and suck up mulm, much easier than sucking gravel.
2 inches outta do. if your planted theres tons of ups hardly any downs, with plants no pockets of anything.
use the proper sands... for non cichlid tanks use tahitian moon, or quikrete premium playsand (home depot) are two i know of for sure. others like building sand have silicates which is bad all around. and the other sands have calcium carbonate which will raise
ph. DONT USE an Under Gravel Filter.
uh...
lots of people use layers of sand and gravel but mostly like soil or laterite or flourite and other subsrates. as a rule epoxy and colored painted gravel is bad in any situation and should not be used
IMO.
thats all i got at the moment