what he said ^^^ i just got some pool filter sand and works great. and is cheappp!!!
i rinsed it out in bucket to get the little the floaty specs out and barely and dust. put it in tank wet before water and didnt cloud up at all, looks great heres a pic of a 10g i put some in.
Most sand is made of crushed coral and clamshell, which obvioulsly makes the water more alkaline. The other problem with sand is that it easily compacts together, eventually getting to be as hard as a rock, and plant roots have a hard time growing in it, and it looses all oxygen in spots that can create methane gas in the worst scenario. A very course sand works better, but there is still a chance of compacting. Give your sand the acid test to find out how alkaline it is.
How many discus and how big is the tank? I did a mistake of using fine sand with discus. Big mistake. Like above mention. Sand compact and will create lots of issue. discus poop a lot and that will mix in with the fine sand. Impossible to clean. If you go with sand, I agree with Robert and go with the bigger coarse sand.